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Visit website Recent posts Updated on $DATE date shaozk Zola2026-09-06T00:00:00+00:00https://shaozk.xyz/atom.xml 2026-09-06T00:00:00+00:00 2026-09-06T00:00:00+00:00 shaozk https://shaozk.xyz/blog/023-the-confusing-python-is-syntax/ <p>我们知道 Python is 语法是用于判断两个变量是否指向同一个对象，也就是说 is 会在内存层面判断否完全相同，而不仅仅是判断值是否相等。</p> <p>但是...</p> <h2 id="li-wai-qing-kuang">例外情况</h2> <pre class="giallo z-code"><code data-lang="python"><span class="giallo-l"><span class="z-source">a</span><span class="z-keyword z-operator"> =</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"><span class="z-source">b</span><span class="z-keyword z-operator"> =</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"><span class="z-support z-function z-builtin z-python">print</span><span class="z-punctuation">(</span><span class="z-meta z-function-call z-arguments z-python">a</span><span class="z-keyword z-control z-flow z-python"> is</span><span class="z-meta z-function-call z-arguments z-python"> b</span><span class="z-punctuation">)</span></span></code></pre> <p>你可以自己尝试在终端输入一下，看一下结果是什么。</p> <p>答案是这段代码会打印 True，然而这似乎和 is 的定义不相符合：从语法上看 a 和 b 是两个独立的变量，且值都是不可变对象字面值常量，其内存地址应该是不一样的才对。</p> <p>这究竟是为什么呢？</p> <h2 id="kai-shi-ai">开始 AI</h2> <blockquote> <p>DeepSeek: CPython 的小整数缓存机制，本质上是 “用空间换时间” 的优化策略：预先创建一批高频使用的小整数对象，让它们在整个解释器生命周期内被共享，避免重复创建和销毁。 缓存范围：不对称的 [-5, 256]</p> </blockquote> <p>本地测试确实是如此，在 -5 到 256 的左闭右闭区间内的整数，都会产生上文提到的例外情况。而只要超出这个范围，就变“正常”了。</p> <p>问题找到答案了，这是 Python 实现机制上的一个技巧，只要记住这个特性就好了。但结果真的是这样吗？</p> <h2 id="yuan-ma-zhi-qian-liao-wu-mi-mi">源码之前，了无秘密</h2> <p>为了加深映像，我决定查看一下 CPython 的源码实现。</p> <pre class="giallo z-code"><code data-lang="c"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// https://github.com/python/cpython/blob/main/Include/internal/pycore_runtime_structs.h</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> _PY_NSMALLPOSINTS</span><span class="z-constant z-numeric"> 1025</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> _PY_NSMALLNEGINTS</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">struct</span><span class="z-source"> _Py_static_objects </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> struct</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> /* Small integers are preallocated in this array so that they</span></span> <span class="giallo-l"><span class="z-comment"> * can be shared.</span></span> <span class="giallo-l"><span class="z-comment"> * The integers that are preallocated are those in the range</span></span> <span class="giallo-l"><span class="z-comment"> * -_PY_NSMALLNEGINTS (inclusive) to _PY_NSMALLPOSINTS (exclusive).</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment"> */</span></span> <span class="giallo-l"><span class="z-source"> PyLongObject small_ints</span><span class="z-punctuation">[</span><span class="z-source">_PY_NSMALLNEGINTS </span><span class="z-keyword z-operator">+</span><span class="z-source"> _PY_NSMALLPOSINTS</span><span class="z-punctuation">];</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> /* ... */</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> singletons</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> _Py_GLOBAL_OBJECT</span><span class="z-punctuation">(</span><span class="z-variable z-parameter">NAME</span><span class="z-punctuation">)</span><span class="z-constant z-character z-escape"> \</span></span> <span class="giallo-l"><span class="z-source"> _PyRuntime</span><span class="z-punctuation">.</span><span class="z-source">static_objects</span><span class="z-punctuation">.</span><span class="z-source">NAME</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> _Py_SINGLETON</span><span class="z-punctuation">(</span><span class="z-variable z-parameter">NAME</span><span class="z-punctuation">)</span><span class="z-constant z-character z-escape"> \</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> _Py_GLOBAL_OBJECT</span><span class="z-punctuation">(</span><span class="z-source">singletons</span><span class="z-punctuation">.</span><span class="z-source">NAME</span><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> _PyLong_SMALL_INTS _Py_SINGLETON</span><span class="z-punctuation">(</span><span class="z-source">small_ints</span><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-modifier">static</span><span class="z-source"> PyObject </span><span class="z-keyword z-operator">*</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">get_small_int</span><span class="z-punctuation">(</span><span class="z-source">sdigit </span><span class="z-variable z-parameter">ival</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> assert</span><span class="z-punctuation">(</span><span class="z-entity z-name z-function">IS_SMALL_INT</span><span class="z-punctuation">(</span><span class="z-source">ival</span><span class="z-punctuation">));</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-punctuation"> (</span><span class="z-source">PyObject </span><span class="z-keyword z-operator">*</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">&amp;</span><span class="z-source">_PyLong_SMALL_INTS</span><span class="z-punctuation">[</span><span class="z-source">_PY_NSMALLNEGINTS </span><span class="z-keyword z-operator">+</span><span class="z-source"> ival</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre> <p>可以看到当值为小整数时，会直接通过 ival + 5 从预先分配好的数组中拿取数据，这也就是小整数共享内存的原因。</p> <h2 id="gen-ai-shuo-de-you-dian-bu-yi-yang">跟 AI 说的有点不一样？</h2> <p>等等，为啥上限值是 1025 而不是 257？最新的 CPython 已经准备将小整数范围修改为 [-5, 1024] 了。</p> <blockquote> <p>Gemini Python 3.13（当前稳定版） / Python 3.14（即将发布）：没有包含此修改。它们的 _PY_NSMALLPOSINTS 依然是旧的 257，小整数池仍为 [-5, 256]。 Python 3.15（开发中版本）：已纳入。这个修改直接合并在 main 开发分支上。按照 Python 每年一个次要版本的发布节奏，包含此变动的 Python 3.15 正式版预计将于 2026 年 10 月左右发布。</p> </blockquote> <p>现在的时间是 2026 年 9 月 14 号，如果我不去看看源码的话，我想很难知道最新的情况。</p> <h2 id="ru-he-bi-mian">如何避免</h2> <p>在判断值是否相等的时候不使用 is，而是使用 ==（也应该这么做）。</p> <h2 id="ling-wai-de-yi-chong-qing-kuang">另外的一种情况</h2> <pre class="giallo z-code"><code data-lang="python"><span class="giallo-l"><span class="z-source">a</span><span class="z-keyword z-operator"> =</span><span class="z-constant z-language z-python"> True</span></span> <span class="giallo-l"><span class="z-source">b</span><span class="z-keyword z-operator"> =</span><span class="z-constant z-language z-python"> True</span></span> <span class="giallo-l"><span class="z-support z-function z-builtin z-python">print</span><span class="z-punctuation">(</span><span class="z-meta z-function-call z-arguments z-python">a</span><span class="z-keyword z-control z-flow z-python"> is</span><span class="z-meta z-function-call z-arguments z-python"> b</span><span class="z-punctuation">)</span></span></code></pre> <p>其答案也是 True，看上去（表现）和小整数一样，但其底层原理却不相同，这里不展开。</p> <h2 id="can-kao">参考</h2> <ul> <li><a rel="external" href="https://zackoverflow.dev/writing/how-often-does-python-allocate">How often does Python allocate?</a></li> </ul> 2026-09-04T00:00:00+00:00 2026-09-04T00:00:00+00:00 shaozk https://shaozk.xyz/blog/022-code-pieces/ <blockquote> <p>注意：个人代码片段记录工具。</p> </blockquote> <h2 id="you-guo-zhe-yang-yi-ge-xiang-fa">有过这样一个想法</h2> <p>一种类似单词卡片的代码卡片工具，支持在 PC 端记录代码片段，然后在手机端查看。可以随时随地查看这些代码片段了（即使在上厕所，当然需要网络）。</p> <p>当时还启动了一个名为 pocket-code（朋友帮忙，意指口袋代码）的个人项目，不过最后不了了之了。其中很重要的一个原因是：我要想后端内容——用户管理和代码数据库设计，还要做前端实现—— Web 网页和手机端 App。</p> <p>这需要的技术栈太多了，我的兴趣还不足以支撑去完成全部内容。</p> <h2 id="you-zhe-yang-yi-ge-xi-guan">有这样一个习惯</h2> <p>我会写一些小代码测试片段，用于验证某个函数或特性。不管是第一份 C 语言的工作，还是后面学习 C++、Qt、Python 等。</p> <p>不过当时没有将其进行管理，永远保存在了公司电脑上（对我来说是如此，但实际上被清空成 0x00000）。</p> <p>于是我痛定思痛，专门 Create 了一个用于存放我示例代码的仓库 <a rel="external" href="https://github.com/shaozk/pieces">pieces</a>，放在 GitHub 上还能防止本地误删（血与泪的教训）。</p> <h2 id="deng-deng">等等？</h2> <p>GitHub 仓库支持部署静态网页，在 PC 和手机都可以访问。代码数据即源代码内容，只要让其以卡片形式显示，我的需求不就实现了么。</p> <p>并且当我在仓库中添加代码并上传到远程仓库时，能自动触发 GitHub Action 完成静态页面更新，不需要我做任何多余动作。</p> <p>简直不要太完美。有了想法，接下来就只剩实现了。</p> <h2 id="shui-lai-shi-xian">谁来实现？</h2> <p>没有 Coding，只有 Vibing。</p> <p>感谢 AI 的开发者们，你们创造了 Eazy 生活。</p> <h2 id="guan-yu-kai-yuan">关于开源</h2> <p>我本意是不打算开源的（也没必要），因为这不是一个通用的工具，只对我自己有用。</p> <p>但奈何 GitHub 仓库不设置成 Public 可见的话，无法正常发布网页，要怪就怪 GitHub。</p> <h2 id="hou-xu-wen-ti">后续问题</h2> <ul> <li> <p>代码量太多导致无法仓库无法存储？</p> <p>我想不可能。</p> </li> <li> <p>分类太少不便于查找？</p> <p>确实有这个问题，目前只按照源代码文件夹（是编程语言名）进行分类，未来或许可以增加更强大的标签管理。</p> </li> <li> <p>交互？</p> <p>目前只有最简单的交互，看上去够用，根据后续的体验再看要不要修改吧。</p> </li> </ul> <p>以上是全部内容，再次感叹 AI 真是给我这种普通程序员巨大的能力，能将一些想法快速实现。</p> <p>PS: 这是网页地址：<a rel="external" href="https://shaozk.github.io/pieces/">code-piece</a></p> 2026-08-10T00:00:00+00:00 2026-08-10T00:00:00+00:00 shaozk https://shaozk.xyz/blog/019-mktime-calc-unix-timestamp/ <p>最近尝试阅读 Linux-0.12 源码，让 AI 帮我挑选一个简单的给我，于是有了本文的内容。</p> <p>在正式介绍之前，有个背景知识需要补充：Linux 使用 1970 年 1 月 1 日作为纪元时间，UNIX 时间戳指的是从这天开始到当前时间的间隔秒数。1970 年 1 月 1 日差不多就是 UNIX 诞生的时间。</p> <p><code>mktime.c</code> 中仅仅只有一个函数 <code>kernel_mktime()</code>，目的是将时间结构体 <code>struct tm</code> 转换为 UNIX 时间戳。</p> <p>代码首先定义了年、日、时、分四个宏，用于将其直接转换称对应秒。</p> <pre class="giallo z-code"><code data-lang="c"><span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> MINUTE</span><span class="z-constant z-numeric"> 60</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> HOUR</span><span class="z-punctuation"> (</span><span class="z-constant z-numeric">60</span><span class="z-keyword z-operator">*</span><span class="z-source">MINUTE</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> DAY</span><span class="z-punctuation"> (</span><span class="z-constant z-numeric">24</span><span class="z-keyword z-operator">*</span><span class="z-source">HOUR</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> YEAR</span><span class="z-punctuation"> (</span><span class="z-constant z-numeric">365</span><span class="z-keyword z-operator">*</span><span class="z-source">DAY</span><span class="z-punctuation">)</span></span></code></pre> <p>这里没有关于月的宏，因为一个月的天数是不定的。这里使用一个长度为 12 的数组，一个元素代表抵达到这个月的时间，并假定为闰年（2 月有 29 天）。</p> <pre class="giallo z-code"><code data-lang="c"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">/* interestingly, we assume leap-years */</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static int</span><span class="z-source"> month</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">12</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre> <p>具体转换方法：</p> <ol> <li> <p>年转换为秒</p> <p>除了年份减去 70 之外，还需要判断当年距 1970 年之间出现了几次闰年，并补上额外的天数。</p> <p>这里有一个很巧妙的方法：(year+1)/4：从 1970 年开始，到 1972 为第一个闰年，但是此时是无需额外补充闰日的，要到 1973 年也就是 (3+1)/4 = 1 才补充一天闰日。</p> <p>注：这里并没有考虑 2000 年及以后的情况。</p> </li> <li> <p>月转换为秒</p> <p>查预先设置好的月份表，因为提前假定是闰年，所以当是平年且月份大于1时，需要额外减去一天时间。</p> </li> <li> <p>日转换为秒</p> <p>因为 tm_mday 取值范围时 1-31，因此在转换时需要减去 1 天（当天还没过去）。</p> <pre class="giallo z-code"><code data-lang="c"><span class="giallo-l"><span class="z-storage z-type">struct</span><span class="z-source"> tm </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_sec</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* seconds after the minute [0-60] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_min</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* minutes after the hour [0-59] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_hour</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* hours since midnight [0-23] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_mday</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* day of the month [1-31] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_mon</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* months since January [0-11] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_year</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* years since 1900 */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_wday</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* days since Sunday [0-6] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_yday</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* days since January 1 [0-365] */</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tm_isdst</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* Daylight Savings Time flag */</span></span> <span class="giallo-l"><span class="z-storage z-type"> long</span><span class="z-source"> tm_gmtoff</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* offset from UTC in seconds */</span></span> <span class="giallo-l"><span class="z-storage z-type"> char</span><span class="z-keyword z-operator"> *</span><span class="z-source">tm_zone</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> /* timezone abbreviation */</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span></code></pre></li> <li> <p>时、分、秒转换为秒</p> <p>直接按照对应宏进行转换。</p> </li> </ol> <p>源码很短，将其全部贴在这里：</p> <pre class="giallo z-code"><code data-lang="c"><span class="giallo-l"><span class="z-punctuation z-definition z-comment">/*</span></span> <span class="giallo-l"><span class="z-comment"> * linux/kernel/mktime.c</span></span> <span class="giallo-l"><span class="z-comment"> *</span></span> <span class="giallo-l"><span class="z-comment"> * (C) 1991 Linus Torvalds</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment"> */</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;time.h&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment">/*</span></span> <span class="giallo-l"><span class="z-comment"> * This isn&#39;t the library routine, it is only used in the kernel.</span></span> <span class="giallo-l"><span class="z-comment"> * as such, we don&#39;t care about years&lt;1970 etc, but assume everything</span></span> <span class="giallo-l"><span class="z-comment"> * is ok. Similarly, TZ etc is happily ignored. We just do everything</span></span> <span class="giallo-l"><span class="z-comment"> * as easily as possible. Let&#39;s find something public for the library</span></span> <span class="giallo-l"><span class="z-comment"> * routines (although I think minix times is public).</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment"> */</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment">/*</span></span> <span class="giallo-l"><span class="z-comment"> * PS. I hate whoever though up the year 1970 - couldn&#39;t they have gotten</span></span> <span class="giallo-l"><span class="z-comment"> * a leap-year instead? I also hate Gregorius, pope or no. I&#39;m grumpy.</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment"> */</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> MINUTE</span><span class="z-constant z-numeric"> 60</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> HOUR</span><span class="z-punctuation"> (</span><span class="z-constant z-numeric">60</span><span class="z-keyword z-operator">*</span><span class="z-source">MINUTE</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> DAY</span><span class="z-punctuation"> (</span><span class="z-constant z-numeric">24</span><span class="z-keyword z-operator">*</span><span class="z-source">HOUR</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#define</span><span class="z-entity z-name z-function"> YEAR</span><span class="z-punctuation"> (</span><span class="z-constant z-numeric">365</span><span class="z-keyword z-operator">*</span><span class="z-source">DAY</span><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">/* interestingly, we assume leap-years */</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static int</span><span class="z-source"> month</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">12</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">29</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">31</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">30</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">long</span><span class="z-entity z-name z-function"> kernel_mktime</span><span class="z-punctuation">(</span><span class="z-storage z-type">struct</span><span class="z-source"> tm </span><span class="z-keyword z-operator">*</span><span class="z-variable z-parameter"> tm</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> long</span><span class="z-source"> res</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> year</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> year </span><span class="z-keyword z-operator">=</span><span class="z-source"> tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_year</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric"> 70</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">/* magic offsets (y+1) needed to get leapyears right.*/</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">=</span><span class="z-source"> YEAR</span><span class="z-keyword z-operator">*</span><span class="z-source">year </span><span class="z-keyword z-operator">+</span><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">((</span><span class="z-source">year</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">/</span><span class="z-constant z-numeric">4</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">+=</span><span class="z-source"> month</span><span class="z-punctuation">[</span><span class="z-source">tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_mon</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">/* and (y+2) here. If it wasn&#39;t a leap-year, we have to adjust */</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_mon</span><span class="z-keyword z-operator">&gt;</span><span class="z-constant z-numeric">1</span><span class="z-keyword z-operator"> &amp;&amp;</span><span class="z-punctuation"> ((</span><span class="z-source">year</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">2</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">%</span><span class="z-constant z-numeric">4</span><span class="z-punctuation">))</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">-=</span><span class="z-source"> DAY</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">+=</span><span class="z-source"> DAY</span><span class="z-keyword z-operator">*</span><span class="z-punctuation">(</span><span class="z-source">tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_mday</span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">+=</span><span class="z-source"> HOUR</span><span class="z-keyword z-operator">*</span><span class="z-source">tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_hour</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">+=</span><span class="z-source"> MINUTE</span><span class="z-keyword z-operator">*</span><span class="z-source">tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_min</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">+=</span><span class="z-source"> tm</span><span class="z-punctuation">-&gt;</span><span class="z-source">tm_sec</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> res</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre> <p>一个比较有趣的彩蛋是：Linus 在注释中说自己讨厌 1970 并吐槽为什么不直接用闰年作为起始年。</p> 2026-08-06T00:00:00+00:00 2026-08-06T00:00:00+00:00 shaozk https://shaozk.xyz/blog/017-create-a-pr-on-github/ <p>想要提 PR 却又忘记了流程，记录一下加深印象。正好有个例子，修改 <a rel="external" href="https://github.com/yhirose/cpp-httplib">httplib</a> 的一个 typo 错误（OS：我真是没事找事）。</p> <ol> <li>在 Github 上 fork 目标仓库</li> <li>克隆 fork 后仓库到本地<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> clone https://github.com/shaozk/cpp-httplib.git</span></span></code></pre></li> <li>切换分支并提交修改内容<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> checkout -b fix_example_typos</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 省略具体提交的内容</span></span></code></pre></li> <li>上传远程仓库<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> push origin fix_example_typos</span></span></code></pre></li> <li>在 Github 上发起 PR 申请，等待 review</li> <li>设置 upstream 为原仓库地址<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> remote add upstream https://github.com/yhirose/cpp-httplib.git</span></span></code></pre></li> <li>拉取 upstream 最新修改<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> fetch upstream</span></span></code></pre></li> <li>切换到主分支并同步 upstream 最新提交<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> checkout master</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> rebase upstream/master</span></span></code></pre></li> <li>更新远程 origin 仓库（Github fork）<pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">git</span><span class="z-string"> push origin master</span></span> <span class="giallo-l"></span></code></pre></li> </ol> <p>其中第 1 5 两步都是在 Gihtub 网页上操作，用鼠标点击即可完成，就省略操作步骤啦。</p> <p>第 6 7 8 9 步是为了同步原仓库的最新提交。</p> 2026-08-06T00:00:00+00:00 2026-08-06T00:00:00+00:00 shaozk https://shaozk.xyz/blog/018-what-is-agentic-ai-from-chatbot-to-co-worker/ <blockquote> <p>原文：https://www.freecodecamp.org/news/what-is-agentic-ai-from-chatbot-to-co-worker</p> </blockquote> <p>你询问 ChatGPT 一个问题，它回答你。你询问另外一个，它再次回答你。这种问答方式一直是大多数人使用 AI 的标准方式：一个能跟你对话，快速且聪明的回答助手。</p> <p>然而一些重大变革正在发生，AI 不再仅仅是回答问题，而是能够独立计划、决策和行动。这类新型 AI 被称作 Agentic AI，在当今科技界正快速地成为最重要的变革之一。</p> <p>本文我们将详细介绍什么是 agentic AI，它的工作原理和应用场景，以及带来的风险。</p> <h1 id="han-gai-de-nei-rong">涵盖的内容</h1> <ul> <li>“Agentic”到底是什么意思？</li> <li>Chatbot 工作原理 vs Agent 工作原理</li> <li>一个真实案例：商务旅行</li> <li>AI Agent 的组成模块</li> <li>为什么变革现在发生？</li> <li>当前 Agentic AI 在哪里使用？</li> <li>有哪些风险？</li> <li>这对你来说意味什么？</li> </ul> <h1 id="agentic-dao-di-shi-shen-me-yi-si">“Agentic”到底是什么意思？</h1> <p>这个单词源自“Agency”：独立行动以实现目标的能力。</p> <p>一个常规的 chatbot 等待你询问问题，而一个 agentic AI 系统是给定一个目标，然后自行找出实现目标的步骤。它能使用工具、浏览网页、编写并运行代码、发送邮件，然后循环往复修复自身的错误，无需你指导具体每一步。</p> <p>思考一下这两种方式的不同：chatbot 像一个知识丰富但只会回答问题的同事；AI agent 像给同事一个任务并告诉他：“帮我解决这个问题”，然后转身离开。</p> <h1 id="chatbot-gong-zuo-yuan-li-vs-agent-gong-zuo-yuan-li">Chatbot 工作原理 vs Agent 工作原理</h1> <p>要理解 agentic AI，看看其行为的区别很有帮助。</p> <p>chatbot 执行一个简单的循环：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>用户输入命令 -&gt; AI 阅读 -&gt; AI 生成恢复 -&gt; 完成</span></span></code></pre> <p>而 AI agent 执行一个更复杂的循环：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>用户指定一个目标</span></span> <span class="giallo-l"><span> —&gt; agent 将其分成多个步骤</span></span> <span class="giallo-l"><span> -&gt; agent 选取一个工具（网页浏览器、代码运行器、邮箱等）</span></span> <span class="giallo-l"><span> -&gt; agent 执行一个动作</span></span> <span class="giallo-l"><span> -&gt; agent 检查结果</span></span> <span class="giallo-l"><span> —&gt; 如果结果错误或未完成，agent 调整并重试</span></span> <span class="giallo-l"><span> -&gt; agent 移动到下一步</span></span> <span class="giallo-l"><span> -&gt; 重复直到完成目标</span></span></code></pre> <p>计划、行动、检查和重试的能力使得 agentic AI 存在本质不同。它不仅仅是在语句中预测下一个单词，而是真正在运行一个小型项目。</p> <h1 id="yi-ge-zhen-shi-an-li-shang-wu-lv-xing">一个真实案例：商务旅行</h1> <p>这里有一个更具体的例子。</p> <p>你告诉 AI agent：“帮我预定下周一去孟买最便宜的航班，找到距离会议中心最近的酒店，并将二者添加到我的日程”。</p> <p>chatbot 会给你链接或建议然后将剩下的全部留给你自己处理。</p> <p>而 AI agent 会：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>Step 1：搜索周一去孟买的航班</span></span> <span class="giallo-l"><span>Step 2：比较价格选择最便宜的方案</span></span> <span class="giallo-l"><span>Step 3：填写乘客信息并完成预定</span></span> <span class="giallo-l"><span>Step 4：搜索会议中心附近的酒店信息</span></span> <span class="giallo-l"><span>Step 5：核对空房情况和价格</span></span> <span class="giallo-l"><span>Step 6：完成酒店预定</span></span> <span class="giallo-l"><span>Step 7：从两个预定中提取确认详情</span></span> <span class="giallo-l"><span>Step 8：添加航班和酒店到你的日程</span></span> <span class="giallo-l"><span>Step 9：给你发送摘要邮件</span></span></code></pre> <p>每一步都涉及使用不同的工具或服务，agent 会帮你处理，你只需要给它一个目标。</p> <h1 id="ai-agent-de-zu-cheng-mo-kuai">AI Agent 的组成模块</h1> <p>每一个 AI agent，不管多复杂，都是由以下核心部份组成。</p> <p><strong>A brain</strong>（大语言模型）：这是推理引擎，常用的大语言模型有 GTP-4 和 Claude。输入目标，思考计划，然后决定下一步做什么。</p> <p><strong>Memory</strong>：agent 需要记住哪些已经完成了。短期记忆跟踪当前任务，长期记忆使 agent 能跨对话存储信息：所以它能够记住你上一次的偏好设置。</p> <p><strong>Tools</strong>：没有工具的 agent 只是 chatbot。工具赋予 agent 真正能力。常用的工具包括网页搜索、代码执行、文件读取、API 调用，邮件和日历访问。agent 决定什么时候使用哪一个工具。</p> <p><strong>A feedback loop</strong>：在执行一个动作之后，agent 会检查其是否工作正常。如果这一步失败或者返回一个错误结果，它将尝试不同的方法。这种自我修正的方式使得 agent 具有处理多步骤任务的能力。</p> <h1 id="wei-shen-me-bian-ge-xian-zai-fa-sheng">为什么变革现在发生？</h1> <p>agentic AI 并不是新概念。研究者对有自主能力的 agent 的研究已有数十年之久，为什么在 2026 年突然无处不在？</p> <p>有三个前提恰好在此时同时满足。</p> <p>首先，语言模型变得更擅长推理。早期模型擅长写作但不擅长逻辑规划。没有一个模型能够处理复杂的任务、找出输出存在的错误，以及更换任务的策略。</p> <p>其次，工具集成变得更加容易。像 LangChain、AutoGen 和 OpenAI 这些框架及其函数调用功能，使得开发者能够轻松将模型连接到实际工具中。之前花费几个月的工程现在只需要几天。</p> <p>再者，企业开始要求更为苛刻。拷贝复制 AI 的建议到论坛或者邮件一下子就过时了。公司希望 AI 能够完成工作流，而不仅仅是协助他们。</p> <h1 id="dang-jin-agentic-ai-zai-na-li-bei-shi-yong">当今 Agentic AI 在哪里被使用？</h1> <p>agentic AI 已经出现在许多行业中，不仅仅是科技公司。</p> <p>在软件开发中，AI agent 编写代码、运行测试、找到 bug 并发起 PR 请求：所有这些只需要单条命令如“修复结账页面的登陆错误”。</p> <p>在客户支持方面，agent 处理所有对话，查询订单历史，处理借款，将复杂案例上报给人工客服，并通过邮件进行后续跟踪：整个过程无需 agent 操作共担。</p> <p>在研究中，agent 搜索批量信息源，提取关键数据，交叉引用核对找到的结果，并生成总结报告。过去通常需要几小时的任务，现在几分钟就能完成。</p> <p>在市场营销方面，agent 负责起草活动内容、安排社交媒体文章、监控绩效指标，并根据有效措施提出调整建议。</p> <h1 id="you-na-xie-feng-xian">有哪些风险？</h1> <p>agentic AI 能力非常强，同时它带来的真实影响是值得深思。</p> <p>其中最大的问题是意外行为。agent 误解目标后会产生一连串的错误步骤，直到人们意识。不像 chatbot 给你一个错误回答可以简单忽略，agent 的错误预订或发送错误邮件已经导致了真实世界的问题。</p> <p>另一个问题时安全。能够读取邮件、访问文件和浏览网页的 agent 极易成为攻击目标。技术上称为：“prompt 注入”：欺骗 agent 在阅读隐藏在网页或文档时执行恶意指令。</p> <p>最后是问责制的问题，当 AI agent 通过十步工作流出错时，非常困难去追溯出错环节以及负责人或责任机制。</p> <p>这是为什么当今大多数设计精妙的 agentic 系统都包括“human in the loop”：在 agent 作出行动之前，一个让人们检阅和提供关键决定的检查点。</p> <h1 id="zhe-dui-ni-lai-shuo-yi-wei-shen-me">这对你来说意味什么？</h1> <p>你无需成为开发人员也能感受到 agentic AI 的影响。这些系统已经集成到了人们日常使用的工具中：邮箱、项目管理应用、CRM 系统等等。</p> <p>值得理解的转变是：AI 正在从一个交互的工具变成了一个与你一起工作的系统。chatbot 回答你的问题，而 agent 则处理你的任务。</p> <p>这是有意义的改变：不仅体现在 AI 的工作原理上，更重要的是我们如何与其一起工作。你越清楚 agent 的能力范围，就越能更好利用它，合理分配任务，更快速找到错误并解决在雪球越滚越大之前。</p> <p>agentic AI 不再只是科幻小说，它已经出现在你的工作场所，并且在未来会变得更强大。</p> <p>理解技术原理是第一步，下一步是决定如何运用在工作中。</p> <p>希望你喜欢这篇文章。</p> 2026-08-05T00:00:00+00:00 2026-08-05T00:00:00+00:00 shaozk https://shaozk.xyz/blog/016-adding-python-application-to-homebrew/ <p>最近看到开源工具 <a rel="external" href="https://github.com/Maciek-roboblog/Claude-Code-Usage-Monitor">claude-monitor</a> 的一个 <a rel="external" href="https://github.com/Maciek-roboblog/Claude-Code-Usage-Monitor/issues/31">issue</a>，目的是希望给工具增加 brew 管理，我想着没事做就尝试了一下。claude-monitor 是一个 Python 应用，是符合 brew 管理<a rel="external" href="https://docs.brew.sh/Language-Specific-Formulae">前提</a>的。</p> <p>不过最终我只在本地完成了测试，没正式往官方提交 PR，只是将生成的 Formula 放在 issue 的评论中（也算是为开源做了贡献吧）。</p> <h1 id="qian-ti-zhi-shi">前提知识</h1> <p><a rel="external" href="https://brew.sh/">Homebrew</a> 是一个 MacOS 常用的开源包管理工具，简称 brew。提供将自己应用添加进 brew 管理的功能，完成后用户就可以直接用 <code>brew install &lt;包名&gt;</code> 下载你的工具了。</p> <p><a rel="external" href="https://docs.brew.sh/Formula-Cookbook#homebrew-terminology">Formula</a> 可以理解为 brew 定义包的方式，你需要为你的应用生成一个专有的 Formula，之后提交 PR 到 <a rel="external" href="https://github.com/Homebrew/brew">brew 的仓库</a>中去，等待管理人员审阅。</p> <h1 id="cao-zuo-bu-zou">操作步骤</h1> <p>使用 <code>brew create</code> 命令，参数为你在 GitHub 上打包好的源码包 URL，另外增加 <code>--python</code> 选项代表指定生成 python 的 Fromula：</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">brew</span><span class="z-string"> create --python https://github.com/Maciek-roboblog/Claude-Code-Usage-Monitor/archive/refs/tags/v4.0.0.tar.gz</span></span></code></pre> <p>执行完输入你的包名：</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">Formula</span><span class="z-string"> name</span><span class="z-source"> [Claude-Code-Usage-Monitor]: claude-monitor</span></span></code></pre> <p>生成对应的 Formula 文件，其绝对路径为：<code>/opt/homebrew/Library/Taps/homebrew/homebrew-core/Formula/c/claude-monitor.rb</code>。内容如下：</p> <pre class="giallo z-code"><code data-lang="ruby"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># Documentation: https://docs.brew.sh/Formula-Cookbook</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># https://docs.brew.sh/rubydoc/Formula</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># PLEASE REMOVE ALL GENERATED COMMENTS BEFORE SUBMITTING YOUR PULL REQUEST!</span></span> <span class="giallo-l"><span class="z-keyword">class</span><span class="z-entity z-name z-type"> ClaudeMonitor</span><span class="z-punctuation"> &lt;</span><span class="z-entity z-other z-inherited-class"> Formula</span></span> <span class="giallo-l"><span class="z-keyword"> include</span><span class="z-support z-class"> Language</span><span class="z-punctuation">::</span><span class="z-support z-class">Python</span><span class="z-punctuation">::</span><span class="z-variable z-other z-constant">Virtualenv</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> desc </span><span class="z-punctuation z-definition z-string z-string">&quot;Real-time Claude Code usage monitor with predictions and warnings&quot;</span></span> <span class="giallo-l"><span class="z-source"> homepage </span><span class="z-punctuation z-definition z-string z-string">&quot;https://github.com/Maciek-roboblog/Claude-Code-Usage-Monitor&quot;</span></span> <span class="giallo-l"><span class="z-source"> url </span><span class="z-punctuation z-definition z-string z-string">&quot;https://github.com/Maciek-roboblog/Claude-Code-Usage-Monitor/archive/refs/tags/v4.0.0.tar.gz&quot;</span></span> <span class="giallo-l"><span class="z-source"> sha256 </span><span class="z-punctuation z-definition z-string z-string">&quot;b1754dd2ede88f2aca56dfa33d9ce7be1d8414ddc467236e98a0584e6d989be9&quot;</span></span> <span class="giallo-l"><span class="z-source"> license </span><span class="z-punctuation z-definition z-string z-string">&quot;MIT&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> depends_on </span><span class="z-punctuation z-definition z-string z-string">&quot;python@3.14&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> # Additional dependency</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> # resource &quot;&quot; do</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> # url &quot;&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> # sha256 &quot;&quot;</span></span> <span class="giallo-l"><span 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class="giallo-l"></span></code></pre> <p>其中 numpy 等包很大，从源码构建需要很长时间，最好替换成预构建好的包。其方式为：<code>depends_on "numpy"</code>。整个修改完成后如下：</p> <pre class="giallo z-code"><code data-lang="ruby"><span class="giallo-l"><span class="z-keyword">class</span><span class="z-entity z-name z-type"> ClaudeMonitor</span><span class="z-punctuation"> &lt;</span><span class="z-entity z-other z-inherited-class"> Formula</span></span> <span class="giallo-l"><span class="z-keyword"> include</span><span class="z-support z-class"> Language</span><span class="z-punctuation">::</span><span class="z-support z-class">Python</span><span class="z-punctuation">::</span><span class="z-variable z-other z-constant">Virtualenv</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> desc </span><span class="z-punctuation z-definition z-string z-string">&quot;Real-time Claude Code usage monitor with predictions and warnings&quot;</span></span> <span class="giallo-l"><span class="z-source"> 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do</span></span> <span class="giallo-l"><span class="z-source"> url </span><span class="z-punctuation z-definition z-string z-string">&quot;https://files.pythonhosted.org/packages/34/74/c6428f875774288bec1396f5bfcbc2d925700a4dad61727fd5f2b12f249d/wcwidth-0.8.2.tar.gz&quot;</span></span> <span class="giallo-l"><span class="z-source"> sha256 </span><span class="z-punctuation z-definition z-string z-string">&quot;91fbef97204b96a3d4d421609b80340b760cf33e26da123ff243d76b1fda8dda&quot;</span></span> <span class="giallo-l"><span class="z-keyword"> end</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> def</span><span class="z-entity z-name z-function"> install</span></span> <span class="giallo-l"><span class="z-variable z-other z-constant"> ENV</span><span class="z-source">[</span><span class="z-punctuation z-definition z-string z-string">&quot;CARGO_NET_GIT_FETCH_WITH_CLI&quot;</span><span class="z-source">]</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation z-definition z-string z-string"> &quot;true&quot;</span></span> <span class="giallo-l"><span class="z-variable z-other z-constant"> ENV</span><span class="z-source">[</span><span class="z-punctuation z-definition z-string z-string">&quot;MATURIN_PEP517&quot;</span><span class="z-source">]</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation z-definition z-string z-string"> &quot;1&quot;</span></span> <span class="giallo-l"><span class="z-source"> virtualenv_install_with_resources</span></span> <span class="giallo-l"><span class="z-keyword"> end</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-support z-function"> test</span><span class="z-keyword"> do</span></span> <span class="giallo-l"><span class="z-support z-function"> system</span><span class="z-source"> bin</span><span class="z-keyword z-operator">/</span><span class="z-punctuation z-definition z-string z-string">&quot;claude-monitor&quot;</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;--version&quot;</span></span> <span class="giallo-l"><span class="z-keyword"> end</span></span> <span class="giallo-l"><span class="z-keyword">end</span></span> <span class="giallo-l"></span></code></pre> <p>然后按照下面三个命令完成本地测试就可以了，整个过程还是比较简单的。</p> <pre class="giallo z-code"><code data-lang="ruby"><span class="giallo-l"><span class="z-variable z-other z-constant">Please</span><span class="z-source"> audit </span><span class="z-keyword z-operator">and</span><span class="z-support z-function"> test</span><span class="z-source"> formula before </span><span class="z-constant z-language">submitting</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-variable z-other z-constant"> HOMEBREW_NO_INSTALL_FROM_API</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric">1</span><span class="z-source"> brew audit </span><span class="z-keyword z-operator">--</span><span class="z-keyword">new</span><span class="z-source"> claude</span><span class="z-keyword z-operator">-</span><span class="z-source">monitor</span></span> <span class="giallo-l"><span class="z-variable z-other z-constant"> HOMEBREW_NO_INSTALL_FROM_API</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric">1</span><span class="z-source"> brew install </span><span class="z-keyword z-operator">--</span><span class="z-source">build</span><span class="z-keyword z-operator">-</span><span class="z-source">from</span><span class="z-keyword z-operator">-</span><span class="z-source">source </span><span class="z-keyword z-operator">--</span><span class="z-source">verbose </span><span class="z-keyword z-operator">--</span><span class="z-source">debug claude</span><span class="z-keyword z-operator">-</span><span class="z-source">monitor</span></span> <span class="giallo-l"><span class="z-variable z-other z-constant"> HOMEBREW_NO_INSTALL_FROM_API</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric">1</span><span class="z-source"> brew </span><span class="z-support z-function">test</span><span class="z-source"> claude</span><span class="z-keyword z-operator">-</span><span class="z-source">monitor</span></span></code></pre> <p>Done!</p> 2026-08-02T00:00:00+00:00 2026-08-02T00:00:00+00:00 shaozk https://shaozk.xyz/blog/015-encode-and-decode-strings/ <p>题目：实现字符串数组到字符串的序列化和反序列化方法，使得输入的字符串数组经过一次编码和一次解码后，仍和原来保持一致。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> encode</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-entity z-name z-type">string</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> strs</span><span class="z-punctuation">) {}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-entity z-name z-type">string</span><span class="z-punctuation">&gt;</span><span class="z-entity z-name z-function"> decode</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {}</span><span class="z-source"> </span></span></code></pre><h1 id="ti-jie">题解</h1> <p>遍历字符串数组，计算每个元素的长度，增加到字符串开头，并增加一个特殊界定符，用于隔开长度和原始字符串：<code>str.size() + '#' + str</code>。</p> <p>字符串中出现了 '#' 符号会不会有影响？</p> <p>答案是不会，关键在于 '#' 第一次出现的位置，这是可以确定的，然后将位置左边的内容解析为长度值，位置往右数长度值个字符的内容解析为原始字符串。</p> <p>看一个例子就比较清晰了：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>5 # h e # # o 5 # w o r l d</span></span> <span class="giallo-l"><span> ^ ^</span></span> <span class="giallo-l"><span> 首个 # 位置 </span></span></code></pre> <p>找到首个 # 位置，解析长度为 5 ，往 # 位置后数 5 个字符，解析字符串为 "he##o"。也就是说，原始字符串中存在 # 符号也不会有任何影响，会被完整解析为字符串。</p> <p>依此类推直到最后一个字符串。这里需要使用的一个技巧是：解析完第一个字符串后，将这部分内容删除，使得解析后续字符串都如同首个一样。</p> <h1 id="dai-ma">代码</h1> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> encode</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-entity z-name z-type">string</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> strs</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> string ret </span><span class="z-keyword z-operator">=</span><span class="z-punctuation z-definition z-string"> &quot;&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-source">string str </span><span class="z-punctuation">:</span><span class="z-source"> strs</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> ret </span><span class="z-keyword z-operator">+=</span><span class="z-entity z-name z-function"> to_string</span><span class="z-punctuation">(</span><span class="z-source">str</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">length</span><span class="z-punctuation">())</span><span class="z-keyword z-operator"> +</span><span class="z-punctuation z-definition z-string z-string"> &quot;#&quot;</span><span class="z-keyword z-operator"> +</span><span class="z-source"> str</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-entity z-name z-type">string</span><span class="z-punctuation">&gt;</span><span class="z-entity z-name z-function"> decode</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-source">string</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> {};</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-keyword z-operator">!</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">empty</span><span class="z-punctuation">()) {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">find</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;#&quot;</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> !=</span><span class="z-entity z-name z-scope-resolution z-cpp"> string</span><span class="z-punctuation">::</span><span class="z-source">npos</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> pos </span><span class="z-keyword z-operator">=</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">find</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;#&quot;</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> len </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> stoi</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">substr</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-source"> pos</span><span class="z-punctuation">));</span></span> <span class="giallo-l"><span class="z-source"> ret</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">push_back</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">substr</span><span class="z-punctuation">(</span><span class="z-source">pos </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-source"> len</span><span class="z-punctuation">));</span></span> <span class="giallo-l"><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">erase</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">substr</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-source"> pos</span><span class="z-punctuation">).</span><span class="z-entity z-name z-function">length</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> +</span><span class="z-constant z-numeric"> 1</span><span class="z-keyword z-operator"> +</span><span class="z-source"> len</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><h1 id="li-cheng">历程</h1> <p>相较于其他算法题，这更像是一个程序员日常需要解决的工程问题。</p> <p>一上来没想那么多，直接使用逗号分隔符号连接字符串数组。很明显，这种方法不能通过测试用例包含逗号分隔符的情况，失败。</p> <p>查看提示，了解到可以通过记录字符串长度进行标识，如何记录字符串长度信息成为关键。但我马上又遇到新的问题；长度本身也占不定长度字符，不好解析。</p> <p>再次审题，发现每个字符串的长度不会超过 200，也就是说三位数字就足以存储所有可能的字符串（不满三位时补充0）。在解析字符串时，前三位固定为长度值，紧接着为原始字符串。很幸运，通过测试。</p> <p>反思，但如果字符串是任意长度，代码就不适应了。查看答案，发现只要在长度和字符串之间增加一个特定符号就可以解决。妙！</p> <h1 id="lian-jie">链接</h1> <ul> <li>https://neetcode.io/problems/string-encode-and-decode/question</li> </ul> 2026-07-31T00:00:00+00:00 2026-07-31T00:00:00+00:00 shaozk https://shaozk.xyz/blog/014-learn-rust-through-rustlings/ <h1 id="bei-jing">背景</h1> <p>在 Zig 创始人 Andrew Kelley 的一次采访中，主持人问到什么是学习 Zig 语言的最好方式时，Andrew 毫不犹豫地提到了 Ziglings。</p> <p>Ziglings 其想法又来自 Rustlings。那么什么是 Rustlings 呢？简单来说：像闯关游戏一样，通过解决一个个代码 bug 来学习编程，每一关都对应一个语言特性，从易到难逐级递进。这样的方式，给学习编程增添了不少趣味。</p> <h1 id="xin-de">心得</h1> <p>我现在已经刷完了 Rustlings 的全部习题，但我直接去阅读 Rust 开源项目仍然够呛，即使有 AI 的辅助。Rustlings 提供的样例相比实际项目使用的太少了，不过 Rustlings 的初衷只是带你入门而已，不应该期望完成了后就精通 Rust。</p> <p>更重要的是我了解到了一种新的学习编程的思路，不一定一开始就要阅读书籍或文档，也可以是通过更有趣的实践方式。</p> <h1 id="lian-jie">链接</h1> <ul> <li><a rel="external" href="https://rustlings.rust-lang.org">Rustlings</a></li> </ul> 2026-07-30T00:00:00+00:00 2026-07-30T00:00:00+00:00 shaozk https://shaozk.xyz/blog/013-use-herdr-instead-of-tmux/ <p>初试 herdr 工具，我有了使用 herdr 替代 tmux 的想法。下面从学习成本、功能覆盖和新特性三个方面说明我为什么这样做。</p> <ol> <li> <p>学习成本</p> <p>作为一个务实派，使用一个新工具首先需要考虑的是学习成本，毕竟程序员都是“懒惰”的。而 herdr 的默认按键绑定和 tmux 基本一样，从 tmux 切换过去非常丝滑。</p> <p>并且，herdr 提供了更丰富的按键提示功能，忘记了马上可以查看提示（我之前使用 tmux 可没少查按键）。</p> </li> <li> <p>功能覆盖</p> <p>能使用的功能必须是一样的，我可不想丢了西瓜捡了芝麻。</p> <p>我用到的 tmux 功能很少，如：新建 window 和 pane，在不同的 window 和 pane 之间切换。对于这些基本窗口管理功能，herdr 全部都提供了。</p> <p>或许有些 tmux 具有的功能 herdr 没有，不过那些我没用到过，也不知道其存在。</p> </li> <li> <p>新特性</p> <p>herdr 还提供了一些很棒的特性，太多了我挑选几个令我印象深刻的功能举例。</p> <p>复制模式：我以前想要复制终端打印的内容，需要使用鼠标选中，然后进行拷贝，十分糟糕。而 herdr 直接支持用 vim 风格方式复制终端内容。</p> <p>插件系统：扩展更丰富的功能，如 herdr-plus 插件，支持自定义快速动作和项目。</p> </li> </ol> <p>当然还有其他很多考虑的点，比如代码是否开源，社区是否活跃，对于 herdr 来说，这些都是肯定的。</p> <p>总结，herdr 不仅仅是用 rust 重写多窗口管理工具这么简单，而是真正解决很多痛点问题。具有如下优点：</p> <ul> <li>极少学习成本，对于学习 tmux 的人来说，无缝切换</li> <li>操作更加简单，更多提示信息帮助你使用</li> <li>支持终端复制模式，自定义插件扩展，更丰富的功能</li> <li>更好的 Agents 交互（对我暂时没用）</li> </ul> <p>tmux 无疑是一款十分优秀的多窗口管理工具，不过后面会减少使用了，因为我有了 herdr。</p> <h1 id="lian-jie">链接</h1> <ul> <li><a rel="external" href="https://herdr.dev">herdr</a></li> <li><a rel="external" href="https://herdrplus.com">herdrplus</a></li> </ul> 2026-07-22T00:00:00+00:00 2026-07-22T00:00:00+00:00 shaozk https://shaozk.xyz/blog/010-the-most-vexing-parse/ <p>https://github.com/p-ranav/cgol/blob/master/include/cgol/utils.hpp#L19</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">return</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">string</span><span class="z-punctuation">((</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">istreambuf_iterator</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">char</span><span class="z-punctuation">&gt;(</span><span class="z-source">stream</span><span class="z-punctuation">)),</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">istreambuf_iterator</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">char</span><span class="z-punctuation">&gt;());</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span></code></pre> <p>问题：为什么第一个参数需要添加额外的括号？</p> <p>这是 C++ 中存在的解析歧义问题，可以看下面这一个简单例子，也是我最容易犯的错误：</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Tmp</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-source"> Tmp</span><span class="z-entity z-name z-function"> t</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <p>这段代码是有问题的，<code>Tmp t();</code> 同时也可以看作函数 t 的声明，无输入参数，返回 Tmp 类型变量。</p> <p>对于编译器来说，这种歧义是无法解决的。不过在 C++11 及以后，可以通过将 () 替换成 {} 解决： <code>Tmp t{}</code>。</p> <p>将其变得更复杂一点点：</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Tmp</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-source"> Tmp</span><span class="z-entity z-name z-function"> t</span><span class="z-punctuation">(</span><span class="z-entity z-name z-function">Tmp</span><span class="z-punctuation">());</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <p>这也会产生歧义，Tmp() 可以被解释为无名的参数，其参数类型是返回 Tmp 的无参函数。</p> <p>我们可以继续增将 () 改成 {} 来解决歧义，但是在 C++11 之前，只能通过增加额外括号来解决 <code>Tmp t((Tmp()));</code>，括号表达式不会被误以为是参数声明。</p> <p>至此，问题的答案很明显了，第一个参数添加额外括号是为了防止歧义。</p> <p>但其实：整个语句中第一个参数就算没有额外的括号，也不会出现歧义。因为 return 关键字确定了后面的语句是对象初始化而不是函数声明。</p> <h1 id="can-kao">参考</h1> <ul> <li>https://en.wikipedia.org/wiki/Most_vexing_parse</li> <li>https://zhuanlan.zhihu.com/p/391558669</li> </ul> 2026-07-22T00:00:00+00:00 2026-07-22T00:00:00+00:00 shaozk https://shaozk.xyz/blog/011-write-blog/ <blockquote> <p>本文主要用于激励自己多写博客!</p> </blockquote> <p>在 2026 年的今天，AI 如此发展迅猛，还需要写技术博客吗？</p> <p>你是一个普通程序员，没有巨人般的思考，没有怪物般的能力。能写的也就是些简单的内容、重复的垃圾，几乎无法创造价值。</p> <p>网上参差不齐的文章，直接被 DeepSeek 吊打，它还能帮你归纳，越问越深。</p> <p>那么，你写的技术博客一没 AI 总结的好，二没人看（即便是新人），那还写个锤子？</p> <p>我的回答是：</p> <ol> <li>对于 AI：承认确实没有 AI 生成的好，但是可以慢慢形成自己的特色，你的对手不是 AI，而是以前的你自己。</li> <li>对于没人看：这不是一蹴而就的，需要大量的时间积累、需高度的专注和打磨。是金子总会发光放在这里或许会比较合适。</li> </ol> <p>对于个人的学习成长，我总结以下几点好处：</p> <ul> <li>积累：AI 好用，但是自己不总结不消化、不反思不记录，还是容易忘，跟抄答案没啥区别。</li> <li>专注：我发现在写文字的时候，会进入一种类似心流的状态，整个人的注意力也会集中。</li> <li>文字：有些人的文字一看就是大佬，让人读了又想读；有些人文字，让人没有任何阅读欲望（我也在其列）。</li> </ul> 2026-07-22T00:00:00+00:00 2026-07-22T00:00:00+00:00 shaozk https://shaozk.xyz/blog/012-read-cgol-source-code/ <p><a rel="external" href="https://github.com/p-ranav/cgol">cgol</a> 是一个使用 C++ 实现的 Conway 生命游戏，在终端通过读取 rle 文件启动。所有文件加在一起都只有 1000 行左右，非常适合入门学习。</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>cgol# cloc .</span></span> <span class="giallo-l"><span> 36 text files.</span></span> <span class="giallo-l"><span> 16 unique files.</span></span> <span class="giallo-l"><span> 40 files ignored.</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>github.com/AlDanial/cloc v 2.08 T=0.01 s (1546.5 files/s, 124976.6 lines/s)</span></span> <span class="giallo-l"><span>--------------------------------------------------------------------------------</span></span> <span class="giallo-l"><span>Language files blank comment code</span></span> <span class="giallo-l"><span>--------------------------------------------------------------------------------</span></span> <span class="giallo-l"><span>C/C++ Header 7 116 77 605</span></span> <span class="giallo-l"><span>C++ 3 26 22 212</span></span> <span class="giallo-l"><span>YAML 1 1 1 115</span></span> <span class="giallo-l"><span>Markdown 3 28 0 60</span></span> <span class="giallo-l"><span>CMake 1 4 0 24</span></span> <span class="giallo-l"><span>Bourne Again Shell 1 0 0 2</span></span> <span class="giallo-l"><span>--------------------------------------------------------------------------------</span></span> <span class="giallo-l"><span>SUM: 16 175 100 1018</span></span> <span class="giallo-l"><span>--------------------------------------------------------------------------------</span></span></code></pre><h1 id="gong-cheng">工程</h1> <p>介绍 C++ 项目工程的内容，与代码实现无关。</p> <h2 id="mu-lu-jie-gou">目录结构</h2> <p>非常典型的 C++ 项目，include 存放头文件，src 存放源文件。samples 目录存放的是 rle 文件。</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>cgol</span></span> <span class="giallo-l"><span>├── CMakeLists.txt</span></span> <span class="giallo-l"><span>├── clang-format.bash // 批量格式化脚本</span></span> <span class="giallo-l"><span>├── include</span></span> <span class="giallo-l"><span>│   └── cgol</span></span> <span class="giallo-l"><span>│   ├── cursor_control.hpp // 光标控制</span></span> <span class="giallo-l"><span>│   ├── cursor_movement.hpp // 光标移动</span></span> <span class="giallo-l"><span>│   ├── grid.hpp // cell 网格</span></span> <span class="giallo-l"><span>│   ├── rle_parser.hpp // rle 文件解析器</span></span> <span class="giallo-l"><span>│   ├── termcolor.hpp // 获取终端颜色</span></span> <span class="giallo-l"><span>│   ├── terminal_size.hpp // 获取终端大小</span></span> <span class="giallo-l"><span>│   └── utils.hpp // 工具类</span></span> <span class="giallo-l"><span>├── samples // 存放 rle 文件目录</span></span> <span class="giallo-l"><span>└── src</span></span> <span class="giallo-l"><span> ├── grid.cpp // cell 网格</span></span> <span class="giallo-l"><span> ├── main.cpp // 主程序入口</span></span> <span class="giallo-l"><span> └── rle_parser.cpp // rle 文件解析器</span></span></code></pre> <p>源项目中还有 LICENSE、.gitignore 和一些 md 文件，因为重点是关注源代码，这些就不过多介绍了。</p> <h2 id="cmake-gou-jian">CMake 构建</h2> <p>使用 CMake 构建，必然需要一个根配置文件 CMakeLists.txt。项目很简单，没有其他子配置文件。</p> <pre class="giallo z-code"><code data-lang="cmake"><span class="giallo-l"><span class="z-keyword">cmake_minimum_required</span><span class="z-source">(VERSION 3.8) </span><span class="z-comment"># CMake 最小版本 3.8</span></span> <span class="giallo-l"><span class="z-keyword">project</span><span class="z-source">(cgol) </span><span class="z-comment"># 项目名 cgol</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"># 根据不同 CMake 版本设置 cgol 描述信息（版本越高内容越详细）</span></span> <span class="giallo-l"><span class="z-keyword">if</span><span class="z-source">(CMAKE_VERSION</span><span class="z-keyword"> VERSION_GREATER_EQUAL</span><span class="z-string"> &quot;3.12&quot;</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-keyword"> project</span><span class="z-source">(cgol VERSION 1.0.0 LANGUAGES CXX</span></span> <span class="giallo-l"><span class="z-source"> HOMEPAGE_URL </span><span class="z-string">&quot;https://github.com/p-ranav/cgol&quot;</span></span> <span class="giallo-l"><span class="z-source"> DESCRIPTION </span><span class="z-string">&quot;Conway&#39;s Game of Life&quot;</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-keyword">elseif</span><span class="z-source">(CMAKE_VERSION</span><span class="z-keyword"> VERSION_GREATER_EQUAL</span><span class="z-string"> &quot;3.9&quot;</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-keyword"> project</span><span class="z-source">(cgol VERSION 1.0.0 LANGUAGES CXX</span></span> <span class="giallo-l"><span class="z-source"> DESCRIPTION </span><span class="z-string">&quot;Conway&#39;s Game of Life&quot;</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-keyword">else</span><span class="z-source">()</span></span> <span class="giallo-l"><span class="z-keyword"> project</span><span class="z-source">(cgol VERSION 1.0.0 LANGUAGES CXX)</span></span> <span class="giallo-l"><span class="z-keyword">endif</span><span class="z-source">()</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"># 未指定发布模式时，默认使用 release 模式</span></span> <span class="giallo-l"><span class="z-keyword">if</span><span class="z-source">(</span><span class="z-keyword">NOT</span><span class="z-source"> CMAKE_BUILD_TYPE)</span></span> <span class="giallo-l"><span class="z-keyword"> set</span><span class="z-source">(CMAKE_BUILD_TYPE Release)</span></span> <span class="giallo-l"><span class="z-keyword">endif</span><span class="z-source">()</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">set</span><span class="z-source">(CMAKE_CXX_FLAGS</span><span class="z-string"> &quot;-Wall -Wextra&quot;</span><span class="z-source">) </span><span class="z-comment"># 启动常见警告和额外警告</span></span> <span class="giallo-l"><span class="z-keyword">set</span><span class="z-source">(CMAKE_CXX_FLAGS_DEBUG</span><span class="z-string"> &quot;-g&quot;</span><span class="z-source">) </span><span class="z-comment"># debug 模式时使用该选项</span></span> <span class="giallo-l"><span class="z-keyword">set</span><span class="z-source">(CMAKE_CXX_FLAGS_RELEASE</span><span class="z-string"> &quot;-O3&quot;</span><span class="z-source">) </span><span class="z-comment"># release 模式使用最高级优化</span></span> <span class="giallo-l"><span class="z-keyword">set</span><span class="z-source">(CMAKE_CXX_STANDARD 11) </span><span class="z-comment"># 使用 c++11 标准</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">include_directories</span><span class="z-source">(include)</span></span> <span class="giallo-l"><span class="z-keyword">add_executable</span><span class="z-source">(cgol </span></span> <span class="giallo-l"><span class="z-source"> src/grid.cpp</span></span> <span class="giallo-l"><span class="z-source"> src/rle_parser.cpp</span></span> <span class="giallo-l"><span class="z-source"> src/main.cpp)</span></span></code></pre><h2 id="ge-shi-hua">格式化</h2> <p>clang-format.bash 和 .clang-format 文件，这两个用来批量格式化项目代码。</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># clang-format.bash</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">find</span><span class="z-string"> ./include ./src -type f</span><span class="z-constant z-character z-escape"> \(</span><span class="z-string"> -iname</span><span class="z-constant z-character z-escape"> \*</span><span class="z-string">.cpp -o -iname</span><span class="z-constant z-character z-escape"> \*</span><span class="z-string">.hpp</span><span class="z-constant z-character z-escape"> \)</span><span class="z-keyword z-operator"> |</span><span class="z-entity z-name z-function"> xargs</span><span class="z-string z-punctuation z-definition z-string"> clang-format -style=&quot;{ColumnLimit : 100}&quot; -i</span></span></code></pre> <p>其作用是：找到 include 和 src 目录下所有后缀名为 .cpp 或 .hpp 的文件，按照 .clang-format 文件进行代码格式化，并动态修改每行字符限制为 100 个。一行命令里，用到了 find、xargs 和 clang-format 三个工具。</p> <h1 id="yuan-ma">源码</h1> <p>本章将逐一介绍每一行代码，从 main 函数开始一点一点抽丝剥茧直到看到整个 cgol 全貌。</p> <h2 id="kua-ping-tai">跨平台</h2> <p>cgol 支持类 Unix（Linux/MacOS） 和 Windows 两个平台，通过判断 _MSC_VER 宏是否定义来编写快平台代码。这类代码在项目中随处可以看到，本文主要讲解类 Unix 的代码。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#if defined</span><span class="z-punctuation">(</span><span class="z-entity z-name z-function">_MSC_VER</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Windows</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#else</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Linux/MacOS</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#endif</span></span></code></pre><h2 id="gong-ju-lei">工具类</h2> <h3 id="cursor-control">cursor_control</h3> <p>功能：显示和隐藏光标。</p> <p>实现：定义 cgol::cursor_hider 类利用 RAII 方法控制光标的显示与隐藏：初始化时隐藏，析构时重新显示。具体实现了静态内联函数 show_console_cursor()，其输入参数为 bool 值，代表是否显示光标。</p> <p>这里需要补充一个知识点：Unix 可以通过往终端发送特定的 ANSI 转义序列来显示与隐藏光标，对应规则为：</p> <ul> <li><code>"\033[?25h"</code> - 显示</li> <li><code>"\033[?25l"</code> - 隐藏</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> show_console_cursor</span><span class="z-punctuation">(</span><span class="z-storage z-type z-storage z-modifier">bool const</span><span class="z-variable z-parameter"> show</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">fputs</span><span class="z-punctuation">(</span><span class="z-source">show </span><span class="z-keyword z-operator">?</span><span class="z-punctuation z-definition z-string"> &quot;</span><span class="z-constant z-character z-escape">\033</span><span class="z-string z-punctuation z-definition z-string">[?25h&quot;</span><span class="z-keyword z-operator"> :</span><span class="z-punctuation z-definition z-string"> &quot;</span><span class="z-constant z-character z-escape">\033</span><span class="z-string z-punctuation z-definition z-string">[?25l&quot;</span><span class="z-punctuation">,</span><span class="z-source"> stdout</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">struct</span><span class="z-entity z-name z-type"> cursor_hider</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> cursor_hider</span><span class="z-punctuation">() {</span><span class="z-entity z-name z-function"> show_console_cursor</span><span class="z-punctuation">(</span><span class="z-constant z-language z-false">false</span><span class="z-punctuation">); }</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> ~cursor_hider</span><span class="z-punctuation">() {</span><span class="z-entity z-name z-function"> show_console_cursor</span><span class="z-punctuation">(</span><span class="z-constant z-language z-true">true</span><span class="z-punctuation">); }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h3 id="cursor-movement">cursor_movement</h3> <p>功能：上下左右任意移动光标。</p> <p>实现：move_up()、move_down()、move_right() 和 move_left() 一组函数。对应 ANSI 转义序列为：</p> <ul> <li>"\033[nA" - 向上 n 行</li> <li>"\033[nB" - 向下 n 行</li> <li>"\033[nC" - 向右 n 行</li> <li>"\033[nD" - 向左 n 行</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> move_up</span><span class="z-punctuation">(</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> lines</span><span class="z-punctuation">) {</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot;</span><span class="z-constant z-character z-escape">\033</span><span class="z-string z-punctuation z-definition z-string">[&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> lines </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;A&quot;</span><span class="z-punctuation">; }</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> move_down</span><span class="z-punctuation">(</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> lines</span><span class="z-punctuation">) {</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot;</span><span class="z-constant z-character z-escape">\033</span><span class="z-string z-punctuation z-definition z-string">[&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> lines </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;B&quot;</span><span class="z-punctuation">; }</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> move_right</span><span class="z-punctuation">(</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> cols</span><span class="z-punctuation">) {</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot;</span><span class="z-constant z-character z-escape">\033</span><span class="z-string z-punctuation z-definition z-string">[&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> cols </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;C&quot;</span><span class="z-punctuation">; }</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> move_left</span><span class="z-punctuation">(</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> cols</span><span class="z-punctuation">) {</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot;</span><span class="z-constant z-character z-escape">\033</span><span class="z-string z-punctuation z-definition z-string">[&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> cols </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;D&quot;</span><span class="z-punctuation">; }</span></span></code></pre><h3 id="terminal-size">terminal_size</h3> <p>功能：获取终端的长宽。</p> <p>实现：利用 ioctl() 函数 和 TIOCGWINSZ 来获取终端大小。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">pair</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">size_t</span><span class="z-punctuation">,</span><span class="z-storage z-type"> size_t</span><span class="z-punctuation">&gt;</span><span class="z-entity z-name z-function"> terminal_size</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-storage z-type"> struct</span><span class="z-entity z-name z-type"> winsize</span><span class="z-source"> size</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> ioctl</span><span class="z-punctuation">(</span><span class="z-source">STDOUT_FILENO</span><span class="z-punctuation">,</span><span class="z-source"> TIOCGWINSZ</span><span class="z-punctuation">,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-source">size</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-punctuation"> {</span><span class="z-keyword z-operator">static_cast&lt;</span><span class="z-storage z-type">size_t</span><span class="z-keyword z-operator">&gt;</span><span class="z-punctuation">(</span><span class="z-source">size</span><span class="z-punctuation">.</span><span class="z-source">ws_row</span><span class="z-punctuation">),</span><span class="z-keyword z-operator"> static_cast&lt;</span><span class="z-storage z-type">size_t</span><span class="z-keyword z-operator">&gt;</span><span class="z-punctuation">(</span><span class="z-source">size</span><span class="z-punctuation">.</span><span class="z-source">ws_col</span><span class="z-punctuation">)};</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline size_t</span><span class="z-entity z-name z-function"> terminal_width</span><span class="z-punctuation">() {</span><span class="z-keyword"> return</span><span class="z-entity z-name z-function"> terminal_size</span><span class="z-punctuation">().</span><span class="z-source">second</span><span class="z-punctuation">; }</span></span></code></pre><h3 id="termcolor">termcolor</h3> <p>功能：控制终端打印不同颜色信息。这是一个仅头文件的三方 C++ 库 <a rel="external" href="https://github.com/ikalnytskyi/termcolor">termcolor.h</a>。</p> <h3 id="util">util</h3> <p>功能：一组工具类，包括读取文件、字符串处理。</p> <ul> <li>read_file()：读取文件。输入为 rle 文件地址。输出为文件内容。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> read_file</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">filename</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">ifstream</span><span class="z-entity z-name z-function"> stream</span><span class="z-punctuation">(</span><span class="z-source">filename</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">stream</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">fail</span><span class="z-punctuation">()) {</span></span> <span class="giallo-l"><span class="z-keyword"> throw</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">runtime_error</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;Error: Could not open file &quot;</span><span class="z-keyword z-operator"> +</span><span class="z-source"> filename</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">string</span><span class="z-punctuation">((</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">istreambuf_iterator</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">char</span><span class="z-punctuation">&gt;(</span><span class="z-source">stream</span><span class="z-punctuation">)),</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">istreambuf_iterator</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">char</span><span class="z-punctuation">&gt;());</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>split_string()：分隔字符串。输入为字符串和分隔符。输出为分隔开的字符串数组。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-entity z-name z-scope-resolution z-template z-call z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-punctuation">&gt;</span><span class="z-entity z-name z-function"> split_string</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">str</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-storage z-modifier"> const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">delimiter</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">string</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> strings</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-scope-resolution z-cpp">string</span><span class="z-punctuation">::</span><span class="z-source">size_type pos </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-scope-resolution z-cpp">string</span><span class="z-punctuation">::</span><span class="z-source">size_type prev </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> ((</span><span class="z-source">pos </span><span class="z-keyword z-operator">=</span><span class="z-source"> str</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">find</span><span class="z-punctuation">(</span><span class="z-source">delimiter</span><span class="z-punctuation">,</span><span class="z-source"> prev</span><span class="z-punctuation">))</span><span class="z-keyword z-operator"> !=</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-scope-resolution z-cpp">string</span><span class="z-punctuation">::</span><span class="z-source">npos</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> strings</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">push_back</span><span class="z-punctuation">(</span><span class="z-source">str</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">substr</span><span class="z-punctuation">(</span><span class="z-source">prev</span><span class="z-punctuation">,</span><span class="z-source"> pos </span><span class="z-keyword z-operator">-</span><span class="z-source"> prev</span><span class="z-punctuation">));</span></span> <span class="giallo-l"><span class="z-source"> prev </span><span class="z-keyword z-operator">=</span><span class="z-source"> pos </span><span class="z-keyword z-operator">+</span><span class="z-source"> delimiter</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // To get the last substring (or only, if delimiter is not found)</span></span> <span class="giallo-l"><span class="z-source"> strings</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">push_back</span><span class="z-punctuation">(</span><span class="z-source">str</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">substr</span><span class="z-punctuation">(</span><span class="z-source">prev</span><span class="z-punctuation">));</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> strings</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>starts_with()：判断字符串前缀。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline bool</span><span class="z-entity z-name z-function"> starts_with</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">string</span><span class="z-punctuation">,</span><span class="z-storage z-modifier"> const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">substring</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> string</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">rfind</span><span class="z-punctuation">(</span><span class="z-source">substring</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> ==</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>ltrim()：裁剪字符串左侧的空格。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> ltrim</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">erase</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">find_if</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">(), [](</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> ch</span><span class="z-punctuation">) {</span><span class="z-keyword"> return</span><span class="z-keyword z-operator"> !</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">isspace</span><span class="z-punctuation">(</span><span class="z-source">ch</span><span class="z-punctuation">); }));</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>rtrim()：裁剪字符串右侧的空格。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> rtrim</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">erase</span><span class="z-punctuation">(</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">find_if</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">rbegin</span><span class="z-punctuation">(),</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">rend</span><span class="z-punctuation">(), [](</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> ch</span><span class="z-punctuation">) {</span><span class="z-keyword"> return</span><span class="z-keyword z-operator"> !</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">isspace</span><span class="z-punctuation">(</span><span class="z-source">ch</span><span class="z-punctuation">); }).</span><span class="z-entity z-name z-function">base</span><span class="z-punctuation">(),</span></span> <span class="giallo-l"><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>trim()：裁剪字符串左右的空格。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline void</span><span class="z-entity z-name z-function"> trim</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> ltrim</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> rtrim</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>ltrim_copy()：裁剪字符串左侧的空格后进行拷贝（不修改源字符串）。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> ltrim_copy</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> ltrim</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> s</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>rtrim_copy()：裁剪字符串右侧的空格后进行拷贝（不修改源字符串）。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> rtrim_copy</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> rtrim</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> s</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>trim_copy()：裁剪字符串左右两侧的空格后进行拷贝（不修改源字符串）。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> trim_copy</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> trim</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> s</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>strip_left()：删除字符串左侧匹配子串的部份。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> strip_left</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">input_string</span><span class="z-punctuation">,</span><span class="z-storage z-modifier"> const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">chars</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">string result </span><span class="z-keyword z-operator">=</span><span class="z-source"> input_string</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">erase</span><span class="z-punctuation">(</span><span class="z-source">result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">find_if</span><span class="z-punctuation">(</span><span class="z-source">result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">(), [</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable z-parameter">chars</span><span class="z-punctuation">](</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> ch</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-keyword z-operator"> !</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">isspace</span><span class="z-punctuation">(</span><span class="z-source">ch</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> and</span><span class="z-punctuation"> (</span><span class="z-source">chars</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">find</span><span class="z-punctuation">(</span><span class="z-source">ch</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> ==</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-scope-resolution z-cpp">string</span><span class="z-punctuation">::</span><span class="z-source">npos</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation"> }));</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> result</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>strip_right()：删除字符串右侧匹配子串的部份。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier">static inline</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-entity z-name z-function"> strip_right</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">input_string</span><span class="z-punctuation">,</span><span class="z-storage z-modifier"> const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">chars</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">string result </span><span class="z-keyword z-operator">=</span><span class="z-source"> input_string</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">erase</span><span class="z-punctuation">(</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">find_if</span><span class="z-punctuation">(</span><span class="z-source">result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">rbegin</span><span class="z-punctuation">(),</span><span class="z-source"> result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">rend</span><span class="z-punctuation">(),</span></span> <span class="giallo-l"><span class="z-punctuation"> [</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable z-parameter">chars</span><span class="z-punctuation">](</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> ch</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-keyword z-operator"> !</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">isspace</span><span class="z-punctuation">(</span><span class="z-source">ch</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> and</span><span class="z-punctuation"> (</span><span class="z-source">chars</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">find</span><span class="z-punctuation">(</span><span class="z-source">ch</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> ==</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-scope-resolution z-cpp">string</span><span class="z-punctuation">::</span><span class="z-source">npos</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation"> })</span></span> <span class="giallo-l"><span class="z-source"> .</span><span class="z-entity z-name z-function">base</span><span class="z-punctuation">(),</span></span> <span class="giallo-l"><span class="z-source"> result</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> result</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <ul> <li>parse_digit_from_char()：字符转整形（OS：为啥不直接使用 c - '0' 转换？）。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-modifier z-storage z-type">static inline size_t</span><span class="z-entity z-name z-function"> parse_digit_from_char</span><span class="z-punctuation">(</span><span class="z-storage z-type">char</span><span class="z-variable z-parameter"> c</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> result</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">stringstream str</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> str </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> c</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> str </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> result</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> result</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><h2 id="he-xin-lei">核心类</h2> <p>核心类只有 rle_parser 和 grid 两个，一个用于解析 rle 文件，另一个表征游戏棋盘。通过 rle_parser 类将 rle 文件解析到 grid 中，通过打印并不断刷新 grid 内容来模拟生命游戏过程。</p> <h3 id="rle-parser">rle_parser</h3> <p>功能：解析 rle 文件并转储为方便使用的结构。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> rle_parser</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">string rle_string_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 原始 RLE 文件内容</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">string name_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // pattern 名</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">string</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> comments_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 文件中所有的注释</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">string author_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // pattern 作者</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> size_x_</span><span class="z-punctuation">{</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">};</span><span class="z-punctuation z-definition z-comment z-comment"> // pattern 行</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> size_y_</span><span class="z-punctuation">{</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">};</span><span class="z-punctuation z-definition z-comment z-comment"> // pattern 列</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">size_t</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> rule_birth_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // e.g., 3 in &quot;B3&quot;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">size_t</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> rule_survival_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // e.g., 23 in &quot;S23&quot;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">string pattern_raw_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // pattern 原始内容, e.g., &quot;25boo85boo$24bo...&quot;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">unsigned char</span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> pattern_2d_array</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 2D 数组表示 pattern_raw_</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 解析名字、作者、注释、pattern 等内容</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> parse_attributes</span><span class="z-punctuation">();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 解析 Conway 生命游戏的 RLE pattern（如 &quot;25boo85boo$24bo...&quot;）2D 字符数组</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> parse_pattern</span><span class="z-punctuation">();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 打印解析后的 pattern — 仅用于调试</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> print</span><span class="z-punctuation">()</span><span class="z-storage z-modifier"> const</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 打开 RLE 文件并解析它的 pattern</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // `grid_size_override` 参数用于覆盖 grid 的大小</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> open</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">rle_string</span><span class="z-punctuation">,</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">pair</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">size_t</span><span class="z-punctuation">,</span><span class="z-storage z-type"> size_t</span><span class="z-punctuation">&gt;</span><span class="z-variable z-parameter"> grid_size_override</span><span class="z-keyword z-operator"> =</span><span class="z-source"> {</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 0</span><span class="z-source">}</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 返回 pattern 中的行数</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 该值为以下两种情况之一：</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 1. 从文件中解析出的值</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 2. 或用户提供的作为覆盖的值</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-entity z-name z-function"> rows</span><span class="z-punctuation">()</span><span class="z-storage z-modifier"> const</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 返回 pattern 中的列数，类似 rows()</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-entity z-name z-function"> cols</span><span class="z-punctuation">()</span><span class="z-storage z-modifier"> const</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 返回一个解析 pattern 后的 2D 数组</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // e.g.,</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // [</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // [baaaab],</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // [ababab],</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // [bbbbbb]</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // ]</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-entity z-name z-scope-resolution z-template z-call z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">unsigned char</span><span class="z-punctuation">&gt;&gt;</span><span class="z-entity z-name z-function"> pattern</span><span class="z-punctuation">()</span><span class="z-storage z-modifier"> const</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span></code></pre><h3 id="grid">grid</h3> <p>功能：游戏棋盘，即代表整个游戏。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> grid</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">unsigned char</span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> grid_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 2D 棋盘, 1 = 活着, 0 = 死亡</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> rows_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 棋盘行数</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> cols_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 棋盘列数</span></span> <span class="giallo-l"><span class="z-source"> rle_parser parser_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // RLE 解析器</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 使用 rle 文件构造生命游戏棋盘类</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 棋盘大小 grid_size 用于建立游戏区域的纬度</span></span> <span class="giallo-l"><span class="z-storage z-modifier"> explicit</span><span class="z-entity z-name z-function"> grid</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">rle_filename</span><span class="z-punctuation">,</span><span class="z-storage z-modifier"> const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">pair</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">size_t</span><span class="z-punctuation">,</span><span class="z-storage z-type"> size_t</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">grid_size</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 返回行数，用于 main.cpp 向上移动光标 </span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-entity z-name z-function"> rows</span><span class="z-punctuation">()</span><span class="z-storage z-modifier"> const</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 显示生命游戏棋盘</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> print</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">ostream</span><span class="z-storage z-modifier z-reference z-cpp"> &amp;</span><span class="z-variable z-parameter">stream</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">cout</span><span class="z-punctuation">)</span><span class="z-storage z-modifier"> const</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 更新生命游戏棋盘</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> tick</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span></code></pre><h2 id="main-han-shu">main() 函数</h2> <p>主函数可以大致分成七步：</p> <ol> <li>定义静态变量 run 标志位，默认为 true，代表正在运行。</li> <li>使用 std::signal() 函数重写 SIGINT 对应的中断函数，函数只干了一件事，将 run 的标志修改为 false，代表结束运行。</li> <li>使用 cgol::cursor_hider 类隐藏光标。</li> <li>判断参数数量 argc 是否合法，不合法则打印帮助信息，然后退出。</li> <li>使用 cgol::terminal_size() 函数获取终端的长宽，用于设置游戏的棋盘大小。</li> <li>初始化 cgol::grid 棋盘类。</li> <li>启动由 run 标志确定的循环，不断进行棋盘显示、睡眠、棋盘更新。</li> </ol> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">(</span><span class="z-storage z-type">int</span><span class="z-variable z-parameter"> argc</span><span class="z-punctuation">,</span><span class="z-storage z-type z-storage z-modifier"> char *</span><span class="z-variable z-parameter">argv</span><span class="z-punctuation">[]) {</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type"> static bool</span><span class="z-source"> run </span><span class="z-keyword z-operator">=</span><span class="z-constant z-language z-true"> true</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">signal</span><span class="z-punctuation">(</span><span class="z-source">SIGINT</span><span class="z-punctuation">, [](</span><span class="z-storage z-type">int</span><span class="z-punctuation">){</span><span class="z-source"> run </span><span class="z-keyword z-operator">=</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">; });</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // Hide console cursor</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> cgol</span><span class="z-punctuation">::</span><span class="z-source">cursor_hider ch</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">argc </span><span class="z-keyword z-operator">&lt;</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Usage: ./main &lt;pattern&gt;.rle</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> EXIT_FAILURE</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // Get terminal size and use as bounding box for game of life grid</span></span> <span class="giallo-l"><span class="z-storage z-modifier z-storage z-type"> const auto</span><span class="z-source"> terminal_size </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-scope-resolution z-cpp"> cgol</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">terminal_size</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> rows </span><span class="z-keyword z-operator">=</span><span class="z-source"> terminal_size</span><span class="z-punctuation">.</span><span class="z-source">first</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation">,</span><span class="z-source"> cols </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> (</span><span class="z-source">terminal_size</span><span class="z-punctuation">.</span><span class="z-source">second</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> /</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // Initialize grid with dimensions {rows, cols}</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> cgol</span><span class="z-punctuation">::</span><span class="z-source">grid</span><span class="z-entity z-name z-function"> grid</span><span class="z-punctuation">(</span><span class="z-source">argv</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">],</span><span class="z-source"> {rows</span><span class="z-punctuation">,</span><span class="z-source"> cols}</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">run</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> grid</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">print</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">this_thread</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">sleep_for</span><span class="z-punctuation">(</span><span class="z-source">std</span><span class="z-punctuation">::</span><span class="z-source">chrono</span><span class="z-punctuation">::</span><span class="z-entity z-name z-function">milliseconds</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">50</span><span class="z-punctuation">));</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> move_up</span><span class="z-punctuation">(</span><span class="z-source">grid</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">rows</span><span class="z-punctuation">());</span></span> <span class="giallo-l"><span class="z-source"> grid</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">tick</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> EXIT_SUCCESS</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <p>以上是全部内容。</p> 2026-07-13T00:00:00+00:00 2026-07-13T00:00:00+00:00 shaozk https://shaozk.xyz/blog/008-meet-the-big-shot/ <p>在编程的世界里，有非常多顶尖程序员，他们或是领导开源项目、或是传播基础知识、或是创业改变世界，成为无数程序员的偶像。我曾经无数次幻想过同顶级的程序员共事，学习他们的编程技巧、思维方式。然而我还未有过这样的经历（我太菜了）。</p> <p>事情遇到了转机，我碰到了这样一位程序员。他满足了我对程序员的所有幻想，他的谈吐、他的文字、他的底蕴，无不让我感叹：我想跟他学习并成为他！如果我不把握机会，可能再也无法遇到这么顶级的程序员了。不！不是可能是一定。</p> <p>于是乎我通过不懈努力（厚脸皮），成功加入了他的个人业余项目，这真的是太棒了！这将成为我程序员职业生涯的重大转折点！</p> <p>兴奋的同时也要保持清醒，并不是说加入了项目就能怎么样，我与大佬之间差距还是很大，路还有很长要走。关键在于借助这个机会，不断和大佬交流学习。</p> 2026-07-12T00:00:00+00:00 2026-07-12T00:00:00+00:00 shaozk https://shaozk.xyz/blog/007-use-bear-for-make/ <p>最近使用 Helix 写 C++ ，为了实现在代码间快速导航，需要在 CMake 构建时额外增加选项 <code>-DCMAKE_EXPORT_COMPILE_COMMANDS=ON</code> 来自动生成 compile_commands.json 文件。</p> <p>然而有些代码直接用 make 构建的，但 make 没有选项支持生成 compile_commands.json 文件（OS：我也不想给它们一一补上 CMakeLists.txt）。</p> <p>这个时候，可以使用 bear 工具：</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">bear</span><span class="z-string"> -- make</span></span></code></pre> <p>执行完命令就会生成 compile_commands.json 文件，我又可以愉快地使用 Helix 了。</p> <p>等等如果连 make 都没有该怎么办呢？Bear 早就帮你想到了。</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">bear</span><span class="z-string"> --</span><span class="z-keyword z-operator"> &lt;</span><span class="z-string">your-build-comman</span><span class="z-source">d</span><span class="z-keyword z-operator">&gt;</span></span></code></pre> <p>任何构建命令 bear 工具都支持，你可以直接把构建命令或构建脚本直接传给 bear 。</p> <h1 id="can-kao">参考</h1> <ul> <li>https://github.com/rizsotto/Bear</li> <li>https://zhuanlan.zhihu.com/p/2003798816588067858</li> <li>https://www.annya.work/bear/bear.html</li> </ul> 2026-07-07T00:00:00+00:00 2026-07-07T00:00:00+00:00 shaozk https://shaozk.xyz/blog/005-function-mutable-default-arg/ <blockquote> <p>无意中刷到的「码农高天」的 Python 视频，尝试一下自己也踩坑了。</p> </blockquote> <p>示例代码如下：</p> <pre class="giallo z-code"><code data-lang="python"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Player</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type z-function z-python"> def</span><span class="z-support z-function z-magic z-python"> __init__</span><span class="z-punctuation">(</span><span class="z-variable z-parameter z-function z-language z-special z-self z-python">self</span><span class="z-punctuation">,</span><span class="z-variable z-parameter"> name</span><span class="z-punctuation">:</span><span class="z-support z-type z-python"> str</span><span class="z-punctuation">,</span><span class="z-variable z-parameter"> items</span><span class="z-punctuation">:</span><span class="z-support z-type z-python"> list</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> []):</span></span> <span class="giallo-l"><span class="z-variable z-language z-special z-self z-python"> self</span><span class="z-punctuation">.</span><span class="z-source">name</span><span class="z-keyword z-operator"> =</span><span class="z-source"> name</span></span> <span class="giallo-l"><span class="z-variable z-language z-special z-self z-python"> self</span><span class="z-punctuation">.</span><span class="z-source">items</span><span class="z-keyword z-operator"> =</span><span class="z-source"> items</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">a</span><span class="z-keyword z-operator"> =</span><span class="z-meta z-function-call z-python"> Player</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;A&quot;</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source">b</span><span class="z-keyword z-operator"> =</span><span class="z-meta z-function-call z-python"> Player</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;B&quot;</span><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">a</span><span class="z-punctuation">.</span><span class="z-source">items</span><span class="z-punctuation">.</span><span class="z-meta z-function-call z-python">append</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;hello&quot;</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source">b</span><span class="z-punctuation">.</span><span class="z-source">items</span><span class="z-punctuation">.</span><span class="z-meta z-function-call z-python">append</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;world&quot;</span><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-support z-function z-builtin z-python">print</span><span class="z-punctuation">(</span><span class="z-meta z-function-call z-arguments z-python">a</span><span class="z-punctuation">.</span><span class="z-meta z-function-call z-arguments z-python">items</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-support z-function z-builtin z-python">print</span><span class="z-punctuation">(</span><span class="z-meta z-function-call z-arguments z-python">b</span><span class="z-punctuation">.</span><span class="z-meta z-function-call z-arguments z-python">items</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> </span></span></code></pre> <p>请问终端打印结果是什么？</p> <p>我下意识给出的答案，包括身边的朋友也是：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>[&#39;hello&#39;]</span></span> <span class="giallo-l"><span>[&#39;world&#39;]</span></span></code></pre> <p>而正确的答案是：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>[&#39;hello&#39;, &#39;world&#39;]</span></span> <span class="giallo-l"><span>[&#39;hello&#39;, &#39;world&#39;]</span></span></code></pre> <p>什么原理？</p> <p>Python 中函数的默认参数，只会被创建一次。也就是说所有使用该默认参数的函数调用，都会共享这个默认值。</p> <p>如果参数是不可变的，这没有影响。但如果参数可变（mutable），那就会掉进如上这类陷阱。</p> <p>修复方法比较简单，将默认参数 <code>[]</code> 修改为 <code>None</code> 。</p> <pre class="giallo z-code"><code data-lang="python"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Player</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type z-function z-python"> def</span><span class="z-support z-function z-magic z-python"> __init__</span><span class="z-punctuation">(</span><span class="z-variable z-parameter z-function z-language z-special z-self z-python">self</span><span class="z-punctuation">,</span><span class="z-variable z-parameter"> name</span><span class="z-punctuation">:</span><span class="z-support z-type z-python"> str</span><span class="z-punctuation">,</span><span class="z-variable z-parameter"> items</span><span class="z-punctuation">:</span><span class="z-support z-type z-python"> list</span><span class="z-keyword z-operator"> =</span><span class="z-constant z-language z-python"> None</span><span class="z-punctuation">):</span></span> <span class="giallo-l"><span class="z-variable z-language z-special z-self z-python"> self</span><span class="z-punctuation">.</span><span class="z-source">name</span><span class="z-keyword z-operator"> =</span><span class="z-source"> name</span></span> <span class="giallo-l"><span class="z-keyword z-control z-flow z-python"> if</span><span class="z-source"> items</span><span class="z-keyword z-operator z-logical z-python"> is</span><span class="z-constant z-language z-python"> None</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-variable z-language z-special z-self z-python"> self</span><span class="z-punctuation">.</span><span class="z-source">items</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> []</span></span> <span class="giallo-l"><span class="z-keyword z-control z-flow z-python"> else</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-variable z-language z-special z-self z-python"> self</span><span class="z-punctuation">.</span><span class="z-source">items</span><span class="z-keyword z-operator"> =</span><span class="z-source"> items</span></span></code></pre> <p>那么为什么要这样设计呢？</p> <ol> <li>一次创建，多次使用。减少创建重复的对象，提高性能</li> <li>提供类似静态变量功能，保持状态</li> </ol> <p><a rel="external" href="https://www.bilibili.com/video/BV1NP4y1g7CT?vd_source=c879317db216a66b04538be69b7cc5b5">video</a></p> 2026-07-05T00:00:00+00:00 2026-07-05T00:00:00+00:00 shaozk https://shaozk.xyz/blog/003-use-string-view-instead-of-string/ <p>C++17 中增加了 std::string_view 新特性，表示非占有数据的字符序列。非占有数据如何理解？</p> <p>主要包含三个关键点：</p> <ol> <li> <p>可以表征字符序列</p> <p>C-Style string 和 C++-Style std::string ，都可以用 std:string_view 表示，默认会进行隐式转换。</p> </li> <li> <p>不占有数据存储空间</p> <p>只存储指向原始数据的指针和长度，不会增加数据拷贝的额外负担。</p> </li> <li> <p>无法对数据进行修改</p> <p>你绝对无法修改其数据内容，这也是名字 <code>view</code> 的由来之一。如果你需要对字符串进行修改，那就不该使用它。</p> </li> </ol> <p>有了这些特性，仅仅使用 std::string_view 作为函数形参，就可以实现类似常量引用的效果，不再需要额外的 const 和 reference 修饰符。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// old</span></span> <span class="giallo-l"><span class="z-storage z-type">void</span><span class="z-entity z-name z-function"> print_str</span><span class="z-punctuation">(</span><span class="z-storage z-modifier">const</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> str</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> str </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// now</span></span> <span class="giallo-l"><span class="z-storage z-type">void</span><span class="z-entity z-name z-function"> print_sv</span><span class="z-punctuation">(</span><span class="z-entity z-name z-scope-resolution z-parameter z-cpp">std</span><span class="z-punctuation">::</span><span class="z-entity z-name z-type">string_view</span><span class="z-variable z-parameter"> sv</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> str </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre> <p>然和在《Effective C++》中学到的经验告诉我们尽量 pass-by-reference 而不是 pass-by-value ，当然前提是传值的开销远大于参数参数时。那么 std::string_view 实例对象占用了多大空间呢？</p> <p>在两大开源编译器 g++ 和 clang++ 的实现中，std:string_view 的数据成员仅有两个，一个是指向字符序列的常量指针，另一个是序列大小。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// gnu g++</span></span> <span class="giallo-l"><span class="z-storage z-type">private</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> _M_len</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-modifier"> const</span><span class="z-source"> _CharT</span><span class="z-keyword z-operator">*</span><span class="z-source"> _M_str</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// llvm clang++</span></span> <span class="giallo-l"><span class="z-storage z-type">private</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-source"> const_pointer data_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // exposition only</span></span> <span class="giallo-l"><span class="z-source"> size_type size_</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // exposition only</span></span></code></pre> <p>在 64 位机器上，仅占用 128 bit(16 bytes) 的空间。pass-by-value 和 pass-by-reference 的开销相差无几。</p> <p>另外，std::string_view 支持哈希，可以直接在 std::unordered_map 及其他字典容器中作为 key 使用。</p> <h1 id="xue-xi">学习</h1> <p>https://en.cppreference.com/cpp/string/basic_string_view https://www.learncpp.com/cpp-tutorial/introduction-to-stdstring_view/ https://learnmoderncpp.com/2024/10/29/when-to-use-stdstring_view/ https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3921.html</p> 2026-07-05T00:00:00+00:00 2026-07-05T00:00:00+00:00 shaozk https://shaozk.xyz/blog/004-add-domain-for-github-pages/ <p>废了老大半天劲，终于在 GitHub Page 上使用上自定义域名 <a rel="external" href="https://shaozk.xyz/">shaozk.xyz</a> 了。</p> <p>下面是踩坑步骤：</p> <h2 id="can-kao-bie-ren-bo-ke-jiu-neng-cheng-gong">参考别人博客就能成功</h2> <blockquote> <p>这是我按照并成功配置的博客，很棒！ 之前还参考了其他很多不错的文章，不过当时都没有成功，就不贴链接了吧。</p> </blockquote> <ul> <li><a rel="external" href="https://blog.csdn.net/qq_34902437/article/details/140298754">【教程】Github Page 添加自定义域名</a></li> </ul> <p>按照博客中的步骤一步步来就能成功，不过我的域名是在阿里云买的，界面有些不一样，不过原理是想通的。</p> <h2 id="geng-zhong-yao-de-shi-xue-xi-dao-zuo-liao-shen-me">更重要的是学习到做了什么</h2> <blockquote> <p>DeepSeek</p> </blockquote> <p>GitHub 提供了一个免费域名 https://shaozk.github.io 和对应的服务器，我要做的事情是将自定义域名映射到服务器上去。</p> <p>在这之前需要在 GitHub 上进行域名验证，可以理解为这是为了确保你是域名的拥有者。操作方法是在域名上增加一条 TXT 记录，证明你确实拥有该域名的控制权。</p> <p>可以在谷歌浏览器中 chrome://net-internals/#dns 查看 DNS 解析结果。</p> <h2 id="wei-shen-me-ke-xing">为什么可行？</h2> <p>不是很理解整个流程，或许就先这样吧。反正已经配置通过了 :)</p> 2026-06-28T00:00:00+00:00 2026-06-28T00:00:00+00:00 shaozk https://shaozk.xyz/blog/002-read-just-for-fun/ <p>读过很多书，但内容到嘴边，硬是说不出。记忆模糊错乱，我想这是不总结的后果吧。</p> <p>一直想总结下阅读感悟，但从未开始过，嗯……就从今天开始吧！</p> <blockquote> <p>小时候的林纳斯就对计算机有极高的兴趣，坐在外公的膝盖帮忙输入程序、研究使用手册并开始编程。</p> </blockquote> <p>回想自己小时候，第一次见到计算机应该是在表哥家的书房，具体记不清几岁了。表哥当时在玩《跑跑卡丁车》，我一下子被吸引住了，那酷炫的卡通人物、刺激的赛车场景、流畅的动画效果，我的天啊！这比手机上的贪吃蛇酷多了。</p> <p>所以，表哥是我获取游戏信息的来源，我几乎在表哥家见证了流行游戏的变化:《赛尔号》、《摩尔庄园》、《弹弹堂》、《穿越火线》。表哥用过的 ID 号 55555 我至今还记得。</p> <p>不过这些都没怎么玩过，我玩过的第一个计算机游戏应该是 4399 小游戏《Q版泡泡堂》，当然是表哥带我玩的。里面有双人模式，连同我姐三人轮流玩，津津有味。</p> <p>这是我对于计算机最初的印象了，当时还是叫它电脑呢……</p> <p>不过对于农村出生的我来说，去表哥家玩游戏已经是接触计算机的全部了。大人们只会给你灌输电脑是毒物的思想，去网吧==坏学生，上网打游戏就是吸食电子毒品。也就是说：去网吧上网是被绝对禁止的，我也确实是 到了大学才开始学习到计算机的知识。</p> <p>但是现在回想一下，当时去网吧的人基本是都是去玩游戏的，会编程的人那时候不会出现在我们乡下的网吧。正如林纳斯所说，现在的孩子把更多的时间花在了玩游戏上，并且沉迷其中:)</p> <blockquote> <p>林纳斯在读大学的时候花了一个暑假把《操作系统：设计与实现》读了很多遍，脱胎换骨，达到了一个全新的高度。</p> </blockquote> <p>自己买了那么多技术书，却从来没有专注读完一本过，有些甚至只读了第一章:(。这么多年学了很多但都不精通，反倒不如把一本书吃透。</p> <p>是时候尝试专心读一本书了。</p> <blockquote> <p>林纳斯最开始只是想在自己的电脑上装一个 Minix 版本的 Unix 系统，但是它的终端却不好用，于是他并开始编写自己 的终端仿真程序，用来登陆学校的计算机看新闻。 为了能够下载和上传文件，又需要编写磁盘驱动。慢慢的功能越来多 ，只要再加把劲，它就能破茧成蝶，变成操作系统了。Linux 诞生了！</p> </blockquote> <p>Linux 项目最开始仅仅是一个终端仿真程序，Unix 项目最开始是丹尼斯和肯想在 PDP-11 计算机上玩《星球大战》。伟大的项目何其相似！</p> <p>兴趣是推动学习进步的好东西，我对计算机的兴趣却似乎越来越少。很糟糕，这样真的很糟糕，我自己还没写多少行代码，就要开始不写代码了（LLM 生成）。</p> <p>网上戏说手写代码是古法编程，但是我还是一个初级程序员，没有得到手搓代码的锻炼呀！我得尝试找找对编程的热爱了。</p> <p>我在网上找到了书中提到的那封开始的邮件原文，CMU 对此进行了维护：http://www.cs.cmu.edu/~awb/linux.history.html</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span> From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds)</span></span> <span class="giallo-l"><span> Newsgroups: comp.os.minix</span></span> <span class="giallo-l"><span> Subject: Gcc-1.40 and a posix-question</span></span> <span class="giallo-l"><span> Message-ID:</span></span> <span class="giallo-l"><span> Date: 3 Jul 91 10:00:50 GMT</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span> Hello netlanders,</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span> Due to a project I&#39;m working on (in minix), I&#39;m interested in the posix</span></span> <span class="giallo-l"><span> standard definition. Could somebody please point me to a (preferably)</span></span> <span class="giallo-l"><span> machine-readable format of the latest posix rules? Ftp-sites would be</span></span> <span class="giallo-l"><span> nice.</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span> The project was obviously linux, so by July 3rd I had started to think</span></span> <span class="giallo-l"><span> about actual user-level things: some of the device drivers were ready,</span></span> <span class="giallo-l"><span> and the harddisk actually worked. Not too much else.</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span> As an aside for all using gcc on minix - [ deleted ]</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span> Just a success-report on porting gcc-1.40 to minix using the 1.37</span></span> <span class="giallo-l"><span> version made by Alan W Black &amp; co.</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span> Linus Torvalds torvalds@kruuna.helsinki.fi </span></span></code></pre> <p>林纳斯一生对编程充满热爱，希望我也能成为这样的一个人吧！</p> 2026-06-18T00:00:00+00:00 2026-06-18T00:00:00+00:00 shaozk https://shaozk.xyz/blog/001-create-your-github-page-with-tabi/ <p>最近在网上看到一个博客主题很不错，于是拿来配置我的个人主页。</p> <p>博客主题叫 tabi，仓库地址为：https://github.com/welpo/tabi。这是主题的源代码， 除此之外，作者还贴心为你准备了一个快速开始样例：https://github.com/welpo/tabi-start 。</p> <h2 id="kuai-su-kai-shi">快速开始</h2> <p>因为 tabi 是基于 Zola 实现的，所以只需在克隆代码后执行：</p> <pre class="giallo z-code"><code data-lang="plain"><span class="giallo-l"><span>$ cd tabi-start</span></span> <span class="giallo-l"><span>$ zola serve</span></span></code></pre> <p>就可以在本地启动站点，默认网址是：http://127.0.0.1:1111</p> <h2 id="zheng-he-dao-github-pages">整合到 Github Pages</h2> <p>因为 Github Pages 原生是不支持 zola 的，所以你需要单独创建一个 Actions 。 官方贴心为你准备了方法：https://github.com/getzola/github-pages 。</p> <p>值得注意的是：在增加完部署 zola 的 action.yml 文件后，记得在 Github 仓库设置 替换默认的部署方式。</p> <h2 id="zong-jie">总结</h2> <p>配置下来我的感觉是：好方便，比 jekyll 那一套好用多了，后续我就使用这个不再折腾了吧。</p> 2025-01-17T00:00:00+00:00 2025-01-17T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/15-vcpkg-manual-download-troubleshooting/ <h2 id="qian-yan">前言</h2> <p>在使用vcpkg工具自动安装三方库时，经常会碰到网络问题，导致无法下载源码包而失败。这个时候上网查资料发现可以通过手动下载三方库源码包来避免这个问题，然而我还是踩坑了……</p> <h2 id="cai-keng">踩坑</h2> <p>事情是这样，我在使用vspkg安装nanosvg库时，遇到错误，截图如下： <img src="/csdn/15_1.png" alt="" /></p> <p>经过一番搜寻，解决方案大概可以总结为：</p> <ol> <li> <p>找到源码包网址并下载（在上面的错误信息中有）</p> </li> <li> <p>将下载好的包放入vcpkg的下载目录： <code>${VPKCG_ROOT}/downloads</code></p> </li> <li> <p>执行无需下载的安装指令： <code>vcpkg install nanosvg --no-download</code></p> </li> </ol> <p>我老老实实按照上面的步骤操作，但问题还是没解决……</p> <h2 id="tiao-keng">跳坑</h2> <p>在我仔细查看错误信息的时候，发现源码包名居然和手动下载的不一样！！！手动下载的包名少了 <code>memononen-</code> 前缀，真是服了！ <img src="/csdn/15_2.png" alt="" /></p> <p><img src="/csdn/15_3.png" alt="" /></p> <p>于是我马上将包名手动修改后再执行步骤3，结果Amazing，成功了！ <img src="/csdn/15_4.png" alt="" /></p> <p>谢天谢地问题总算是解决了，值得一提的是 <code>memononen</code> 是该开源库的作者。</p> <h2 id="zong-jie">总结</h2> <p>在后面一些其他手动下载源码包的案例中，我发现不仅仅是前缀有差异，还有各种各样的不同。所以在修改的时候最好直接复制包名，该 <code>Ctrl-C+V</code> 的时候可以 <code>Ctrl-C+V</code> 。</p> <p>不知道这算不算是vcpkg的一个bug，反正手动下载就会遇到这个问题。希望早日所有三方库能自动下载不报错！</p> 2024-12-29T00:00:00+00:00 2024-12-29T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/14-two-sum-ii-input-array-is-sorted/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给你一个下标从 <code>1</code> 开始的整数数组 <code>numbers</code> ，该数组已按非递减顺序排列，请你从数组中找到满足相加之和等于目标数 <code>target</code> 的两个数。如果社这两个数分别是 <code>numbers[index1]</code> 和 <code>numbers[index2]</code> ，则 <code>1&lt;=index1&lt;index2&lt;=numbers.length</code> 。</p> <p>以长度为 <code>2</code> 的整数数组 <code>[index1,index2]</code> 的形式返回这两个整数的下标 <code>index1</code> 和 <code>index2</code> 。</p> <p>可以假设每个输入只对应唯一的答案，而且你不可以重复使用相同的元素。</p> <p>你所设计的解决方案只使用常量级的额外空间。</p> <p>原题链接： <a rel="external" href="https://leetcode.cn/problems/two-sum-ii-input-array-is-sorted/">167. 两数之和 II - 输入有序数组</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-bao-li-fa">1 暴力法</h3> <h4 id="fen-xi">分析</h4> <p>因为需要查询两个值，马上可以想到使用两层遍历来分别查询结果。对于第一层循环，需要整个遍历数组，因为任何一个元素都有可能是结果之一；假定其中一个值下标为 <code>index1</code> ，则可以在剩下的数组中查找值为 <code>target-numbers[index1]</code> 的元素，其下标值即为需要查找的 <code>index2</code> 。</p> <p>由题意已知数组已排序，可使用二分查找法提高查询速度。</p> <h4 id="dai-ma">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> find</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> vec</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> left</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> right</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> n</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 二分查找</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> ret </span><span class="z-keyword z-operator">= -</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> mid </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">left </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> right</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> mid </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> (</span><span class="z-source">left </span><span class="z-keyword z-operator">+</span><span class="z-source"> right</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> /</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">vec</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">mid</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> ==</span><span class="z-source"> n</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-source"> mid</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> break</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else if</span><span class="z-punctuation"> (</span><span class="z-source">vec</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">mid</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> &gt;</span><span class="z-source"> n</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> right </span><span class="z-keyword z-operator">=</span><span class="z-source"> mid</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> left </span><span class="z-keyword z-operator">=</span><span class="z-source"> mid </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type"> vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-entity z-name z-function"> twoSum</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> numbers</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> target</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> idx1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> idx2 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> num </span><span class="z-keyword z-operator">=</span><span class="z-source"> numbers</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-source">idx1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> idx1 </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> num</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">idx1</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组</span></span> <span class="giallo-l"><span class="z-source"> idx2 </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> find</span><span class="z-punctuation">(</span><span class="z-source">numbers</span><span class="z-punctuation">,</span><span class="z-source"> idx1 </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-source"> num</span><span class="z-punctuation">,</span><span class="z-source"> target </span><span class="z-keyword z-operator">-</span><span class="z-source"> numbers</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">idx1</span><span class="z-punctuation">));</span><span class="z-punctuation z-definition z-comment z-comment"> // 二分查找</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">idx2 </span><span class="z-keyword z-operator">!= -</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">) {</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> break</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 找到直接终止循环</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-punctuation"> {</span><span class="z-source">idx1 </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-source"> idx2 </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">};</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(logn)</code> ，遍历第一个元素需要 <code>O(n)</code> 时间，查找第二个元素需要 <code>O(logn)</code> 时间；二者结合 <code>O(nlogn)</code></p> </li> <li> <p>空间复杂度： <code>O(1)</code> ，只使用常量空间。</p> </li> </ul> <h3 id="2-shuang-zhi-zhen">2 双指针</h3> <h4 id="fen-xi-1">分析</h4> <p>已知结果唯一且数组有序，因此可以设定两个指针分别指向数组的首尾，指针从两头往中间靠拢，直到找到满足条件的结果。当两指针指向元素和为结果值，返回结果；当元素和小于结果值，更新左指针（++）；当元素和大于结果值，更新右指针（–）。</p> <h4 id="dai-ma-1">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-entity z-name z-function"> twoSum</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> numbers</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> target</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> idx1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> idx2 </span><span class="z-keyword z-operator">=</span><span class="z-source"> numbers</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 定义指向首尾的指针</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">idx1 </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> idx2</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组</span></span> <span class="giallo-l"><span class="z-storage z-type"> auto</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-source"> numbers</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">idx1</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> +</span><span class="z-source"> numbers</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">idx2</span><span class="z-punctuation">);</span><span class="z-punctuation z-definition z-comment z-comment"> // 计算两数和</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">sum </span><span class="z-keyword z-operator">==</span><span class="z-source"> target</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否是目标值</span></span> <span class="giallo-l"><span class="z-keyword"> break</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else if</span><span class="z-punctuation"> (</span><span class="z-source">sum </span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> target</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否比目标值大</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> --</span><span class="z-source">idx2</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新idx2</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否比目标值小</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">idx1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新idx1</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-punctuation"> {</span><span class="z-source">idx1 </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-source"> idx2 </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">};</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回结果数组（需要替换为从1开始的下标）</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du-1">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(n)</code> ，双指针移动的总次数不超过 <code>n</code></p> </li> <li> <p>空间复杂度： <code>O(1)</code> ，常量空间使用。</p> </li> </ul> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li> <p>当需要在有序数组上进行查询操作时，二分查找是个不错的选择。</p> </li> <li> <p>双指针法也适合在有序数组上使用。</p> </li> </ul> <hr /> 2024-12-18T00:00:00+00:00 2024-12-18T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/13-gopl-chapter-1-tutorial/ <h2 id="1-ru-men">1.入门</h2> <h3 id="lian-xi-ti">练习题</h3> <h4 id="1-1">1.1</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习1.1: 修改 echo 程序，使其能够打印 os.Args[0]，即被执行命令本身的名字。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">package main</span><span class="z-punctuation z-definition z-comment z-comment"> // 声明包</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入包fmt（格式化输出）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入包os（获取命令行参数）</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span><span class="z-punctuation z-definition z-comment z-comment"> // 主函数</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 打印所有参数（包括程序本身）</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 输出</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 注：符号‘#’除注释外，还代表输入的命令</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 进入到.go源文件所在目录，输入go build即可运行（无需指定源文件）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># -o 用于指定生成的可执行文件（默认以文件夹名作为文件名）</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_1#</span><span class="z-string"> go build -o a.out</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_1#</span><span class="z-string"> ./a.out arg1 arg2 arg3</span></span> <span class="giallo-l"><span class="z-punctuation">[</span><span class="z-source">./a.out arg1 arg2 arg3</span><span class="z-punctuation">]</span></span> <span class="giallo-l"></span></code></pre><h4 id="1-2">1.2</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.2: 修改 echo 程序，使其打印每个参数的索引和值，每个一行。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> idx</span><span class="z-punctuation">,</span><span class="z-source"> value</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历命令行参数</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-source">idx</span><span class="z-punctuation">,</span><span class="z-source"> value</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 打印索引和参数</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 编译命令同上，故省略</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_2#</span><span class="z-string"> ./a.out arg1 arg2 arg3</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0</span><span class="z-string"> ./a.out</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-string"> arg1</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-string"> arg2</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-string"> arg3</span></span></code></pre><h4 id="1-3">1.3</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.3: 做实验测量潜在低效的版本和使用了 strings.Join 的版本的运行时间差异。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;time&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入包time（计时器）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;strings&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入包strings（字符串）</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-source"> start1</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Now</span><span class="z-punctuation">()</span><span class="z-punctuation z-definition z-comment z-comment"> // 计时器1，用于计算老方法时间开销</span></span> <span class="giallo-l"><span class="z-source"> str</span><span class="z-punctuation">,</span><span class="z-source"> sep</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-punctuation z-definition z-string"> &quot;&quot;</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string"> &quot;&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化str存储连接后的字符串，初始化sep存储空格</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> arg</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> str </span><span class="z-keyword z-operator">+=</span><span class="z-source"> sep </span><span class="z-keyword z-operator">+</span><span class="z-source"> arg</span><span class="z-punctuation z-definition z-comment z-comment"> // 连接参数字符串</span></span> <span class="giallo-l"><span class="z-source"> sep </span><span class="z-keyword z-operator">=</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 经过一个参数后，sep换为空格</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-source">str</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 输出连接后的值</span></span> <span class="giallo-l"><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;old way: %dns elapsed</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Since</span><span class="z-punctuation">(</span><span class="z-source">start1</span><span class="z-punctuation">).</span><span class="z-entity z-name z-function">Nanoseconds</span><span class="z-punctuation">())</span><span class="z-punctuation z-definition z-comment z-comment"> // 打印时间开销</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> start2</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Now</span><span class="z-punctuation">()</span><span class="z-punctuation z-definition z-comment z-comment"> // 计时器2，用于计算新方法时间开销</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-source">strings</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Join</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">))</span><span class="z-punctuation z-definition z-comment z-comment"> // 输出连接后的值</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;new way: %dns elapsed</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Since</span><span class="z-punctuation">(</span><span class="z-source">start2</span><span class="z-punctuation">).</span><span class="z-entity z-name z-function">Nanoseconds</span><span class="z-punctuation">())</span><span class="z-punctuation z-definition z-comment z-comment"> // 打印时间开销</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_3#</span><span class="z-string"> go build -o a.out</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_3#</span><span class="z-string"> ./a.out arg1 arg2 arg3</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">./a.out</span><span class="z-string"> arg1 arg2 arg3</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">old</span><span class="z-string"> way: 113583ns elapsed</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">./a.out</span><span class="z-string"> arg1 arg2 arg3</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">new</span><span class="z-string"> way: 2584ns elapsed</span></span></code></pre><h4 id="1-4">1.4</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.4: 修改 dup2，出现重复的行时打印文件名称</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Dup2 prints the count and text of lines that appear more than once</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// in the input. It reads from stdin or from a list of named files.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;bufio&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入bufio包（标准输入）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 自定义计数器</span></span> <span class="giallo-l"><span class="z-source">type MyCount </span><span class="z-storage z-type">struct</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> count</span><span class="z-storage z-type"> int</span><span class="z-punctuation z-definition z-comment z-comment"> // 记录行数</span></span> <span class="giallo-l"><span class="z-source"> names []string</span><span class="z-punctuation z-definition z-comment z-comment"> // 记录行所在文件</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-source"> counts</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> make</span><span class="z-punctuation">(</span><span class="z-source">map</span><span class="z-punctuation">[</span><span class="z-source">string</span><span class="z-punctuation">]</span><span class="z-keyword z-operator">*</span><span class="z-source">MyCount</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 构造&lt;string,MyCount*&gt;字典</span></span> <span class="giallo-l"><span class="z-source"> files</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-source">:</span><span class="z-punctuation">]</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-entity z-name z-function"> len</span><span class="z-punctuation">(</span><span class="z-source">files</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> ==</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否包含文件</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> countLines</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stdin</span><span class="z-punctuation">,</span><span class="z-source"> counts</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 从标准输入获取行</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> arg</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range files </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> f</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Open</span><span class="z-punctuation">(</span><span class="z-source">arg</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 打开文件</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;dup2: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> continue</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> countLines</span><span class="z-punctuation">(</span><span class="z-source">f</span><span class="z-punctuation">,</span><span class="z-source"> counts</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 从文件获取行</span></span> <span class="giallo-l"><span class="z-source"> f</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Close</span><span class="z-punctuation">()</span><span class="z-punctuation z-definition z-comment z-comment"> // 关闭文件</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> printLines</span><span class="z-punctuation">(</span><span class="z-source">counts</span><span class="z-punctuation">,</span><span class="z-entity z-name z-function"> len</span><span class="z-punctuation">(</span><span class="z-source">files</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> !=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 输出字典</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 构建以字符串为值、以自定义计数器为键的map</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 按行获取字符串，判断map中是否包含该字符串，是则计数+1，将文件名添加到列表中（如果不存在）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 否则新键一个键值对插入到map中</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [in] f 文件</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [out] counts 自定义计数器map </span></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> countLines</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">f</span><span class="z-storage z-modifier"> *</span><span class="z-entity z-name z-type">os</span><span class="z-source">.</span><span class="z-variable z-parameter">File</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> counts</span><span class="z-variable z-parameter"> map</span><span class="z-punctuation">[</span><span class="z-source">string</span><span class="z-punctuation">]</span><span class="z-storage z-modifier">*</span><span class="z-variable z-parameter">MyCount</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> input</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> bufio</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">NewScanner</span><span class="z-punctuation">(</span><span class="z-source">f</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> input</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Scan</span><span class="z-punctuation">() {</span><span class="z-punctuation z-definition z-comment z-comment"> // 按行扫描</span></span> <span class="giallo-l"><span class="z-source"> line</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> input</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Text</span><span class="z-punctuation">()</span><span class="z-punctuation z-definition z-comment z-comment"> // 获取文本</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> ok</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">];</span><span class="z-source"> ok </span><span class="z-punctuation">{</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果字典中存在该字符串</span></span> <span class="giallo-l"><span class="z-source"> counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">].</span><span class="z-source">count</span><span class="z-keyword z-operator">++</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 计数加1</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-keyword z-operator"> !</span><span class="z-entity z-name z-function">contains</span><span class="z-punctuation">(</span><span class="z-source">counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">].</span><span class="z-source">names</span><span class="z-punctuation">,</span><span class="z-source"> f</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Name</span><span class="z-punctuation">()) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否已经包含文件名</span></span> <span class="giallo-l"><span class="z-source"> counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">].</span><span class="z-source">names</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">].</span><span class="z-source">names</span><span class="z-punctuation">,</span><span class="z-source"> f</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Name</span><span class="z-punctuation">())</span><span class="z-punctuation z-definition z-comment z-comment"> // 添加文件名</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> = &amp;</span><span class="z-source">MyCount</span><span class="z-punctuation">{</span><span class="z-punctuation z-definition z-comment z-comment"> // 插入新键-值对</span></span> <span class="giallo-l"><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-comment z-comment"> // 计数为1</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> make</span><span class="z-punctuation">([]</span><span class="z-source">string, 1), // 空的字符串数组</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-source"> counts</span><span class="z-punctuation">[</span><span class="z-source">line</span><span class="z-punctuation">].</span><span class="z-source">names</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-source"> f</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Name</span><span class="z-punctuation">()</span><span class="z-punctuation z-definition z-comment z-comment"> // 填充字符串数组</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // NOTE: ignoring potential errors from input.Err()</span></span> <span class="giallo-l"><span class="z-source">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 根据是否是文件输出自定义计数器map</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [in] counts 自定义计数器map</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [in] flagFile 文件标志</span></span> <span class="giallo-l"><span class="z-source">func</span><span class="z-entity z-name z-function"> printLines</span><span class="z-punctuation">(</span><span class="z-source">counts map</span><span class="z-punctuation">[</span><span class="z-source">string</span><span class="z-punctuation">]</span><span class="z-keyword z-operator">*</span><span class="z-source">MyCount</span><span class="z-punctuation">,</span><span class="z-source"> flagFile</span><span class="z-storage z-type"> bool</span><span class="z-punctuation">)</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> line</span><span class="z-punctuation">,</span><span class="z-source"> c :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range counts {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> c</span><span class="z-punctuation">.</span><span class="z-source">count</span><span class="z-keyword z-operator"> &gt;</span><span class="z-constant z-numeric"> 1</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> flagFile {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否由文件读取</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%d</span><span class="z-constant z-character z-escape">\t</span><span class="z-string">%s</span><span class="z-constant z-character z-escape">\t</span><span class="z-string">%v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> c</span><span class="z-punctuation">.</span><span class="z-source">count</span><span class="z-punctuation">,</span><span class="z-source"> line</span><span class="z-punctuation">,</span><span class="z-source"> c</span><span class="z-punctuation">.</span><span class="z-source">names</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> }</span><span class="z-keyword"> else</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%d</span><span class="z-constant z-character z-escape">\t</span><span class="z-string">%s</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> c</span><span class="z-punctuation">.</span><span class="z-source">count</span><span class="z-punctuation">,</span><span class="z-source"> line</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-source">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 判断字符串数组是否包含某一个字符串(暴力法)</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [in] slice 字符串数组</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [in] s 字符串</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// [out] 返回是否包含</span></span> <span class="giallo-l"><span class="z-source">func</span><span class="z-entity z-name z-function"> contains</span><span class="z-punctuation">(</span><span class="z-source">slice []string</span><span class="z-punctuation">,</span><span class="z-source"> s string</span><span class="z-punctuation">)</span><span class="z-storage z-type"> bool</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> value :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range slice {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> value </span><span class="z-keyword z-operator">==</span><span class="z-source"> s {</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-true"> true</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source">}</span></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_4#</span><span class="z-string"> cat test1.txt</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">b</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">b</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">c</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_4#</span><span class="z-string"> cat test2.txt</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">a</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">a</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">b</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">b</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">b</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">c</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_4#</span><span class="z-string"> ./a.out test1.txt test2.txt</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-string"> c</span><span class="z-source"> [test1.txt</span><span class="z-string"> test2.txt]</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-string"> a</span><span class="z-source"> [test2.txt]</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">5</span><span class="z-string"> b</span><span class="z-source"> [test1.txt</span><span class="z-string"> test2.txt]</span></span></code></pre><h4 id="1-5">1.5</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.5: 修改前面的Lissajous程序里的调色板，由黑色改为绿色。</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 我们可以用color.RGBA{0xRR, 0xGG, 0xBB, 0xff}来得到#RRGGBB这个色值，</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 三个十六进制的字符串分别代表红、绿、蓝像素。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Lissajous generates GIF animations of random Lissajous figures.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入image包（图像处理）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image/color&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入image下的子包color（颜色）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image/gif&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入gif包（动图）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;math&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入math包（数学）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;math/rand&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 导入rand包（随机数）</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;time&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">var palette </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> []</span><span class="z-source">color.Color</span><span class="z-punctuation">{</span><span class="z-source">color</span><span class="z-punctuation">.</span><span class="z-source">White</span><span class="z-punctuation">,</span><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">Black</span><span class="z-punctuation">,</span><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">}}</span><span class="z-punctuation z-definition z-comment z-comment"> // 颜色数组</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-modifier">const</span><span class="z-punctuation"> (</span></span> <span class="giallo-l"><span class="z-source"> whiteIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation z-definition z-comment z-comment"> // first color in palette</span></span> <span class="giallo-l"><span class="z-source"> blackIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation z-definition z-comment z-comment"> // next color in palette</span></span> <span class="giallo-l"><span class="z-source"> greenIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation z-definition z-comment z-comment"> // 绿色</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // The sequence of images is deterministic unless we seed</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // the pseudo-random number generator using the current time.</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // Thanks to Randall McPherson for pointing out the omission.</span></span> <span class="giallo-l"><span class="z-source"> rand</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Seed</span><span class="z-punctuation">(</span><span class="z-source">time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Now</span><span class="z-punctuation">().</span><span class="z-entity z-name z-function">UTC</span><span class="z-punctuation">().</span><span class="z-entity z-name z-function">UnixNano</span><span class="z-punctuation">())</span><span class="z-punctuation z-definition z-comment z-comment"> // 使用当前时间生成随机数</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> lissajous</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stdout</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> lissajous</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">out io</span><span class="z-source">.</span><span class="z-variable z-parameter">Writer</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-modifier"> const</span><span class="z-punctuation"> (</span></span> <span class="giallo-l"><span class="z-source"> cycles </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 5</span><span class="z-punctuation z-definition z-comment z-comment"> // number of complete x oscillator revolutions</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.001</span><span class="z-punctuation z-definition z-comment z-comment"> // angular resolution</span></span> <span class="giallo-l"><span class="z-source"> size </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation z-definition z-comment z-comment"> // image canvas covers [-size..+size]</span></span> <span class="giallo-l"><span class="z-source"> nframes </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 64</span><span class="z-punctuation z-definition z-comment z-comment"> // number of animation frames</span></span> <span class="giallo-l"><span class="z-source"> delay </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 8</span><span class="z-punctuation z-definition z-comment z-comment"> // delay between frames in 10ms units</span></span> <span class="giallo-l"><span class="z-punctuation"> )</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> freq</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> rand</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Float64</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> *</span><span class="z-constant z-numeric"> 3.0</span><span class="z-punctuation z-definition z-comment z-comment"> // relative frequency of y oscillator</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> gif</span><span class="z-punctuation">.</span><span class="z-source">GIF</span><span class="z-punctuation">{</span><span class="z-source">LoopCount</span><span class="z-punctuation">:</span><span class="z-source"> nframes</span><span class="z-punctuation">}</span></span> <span class="giallo-l"><span class="z-source"> phase</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.0</span><span class="z-punctuation z-definition z-comment z-comment"> // phase difference</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> i</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> nframes</span><span class="z-punctuation">;</span><span class="z-source"> i</span><span class="z-keyword z-operator">++</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> rect</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> image</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Rect</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 2</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 2</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> img</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> image</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">NewPaletted</span><span class="z-punctuation">(</span><span class="z-source">rect</span><span class="z-punctuation">,</span><span class="z-source"> palette</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> t</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.0</span><span class="z-punctuation">;</span><span class="z-source"> t </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> cycles</span><span class="z-keyword z-operator">*</span><span class="z-constant z-numeric">2</span><span class="z-keyword z-operator">*</span><span class="z-source">math</span><span class="z-punctuation">.</span><span class="z-source">Pi</span><span class="z-punctuation">;</span><span class="z-source"> t </span><span class="z-keyword z-operator">+=</span><span class="z-source"> res </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> x</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> math</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Sin</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> y</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> math</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Sin</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-keyword z-operator">*</span><span class="z-source">freq </span><span class="z-keyword z-operator">+</span><span class="z-source"> phase</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> img</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">SetColorIndex</span><span class="z-punctuation">(</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-storage z-type">int</span><span class="z-punctuation">(</span><span class="z-source">x</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">0.5</span><span class="z-punctuation">),</span><span class="z-source"> size</span><span class="z-keyword z-operator">+</span><span class="z-storage z-type">int</span><span class="z-punctuation">(</span><span class="z-source">y</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">0.5</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> greenIndex</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> phase </span><span class="z-keyword z-operator">+=</span><span class="z-constant z-numeric"> 0.1</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation">.</span><span class="z-source">Delay</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">anim</span><span class="z-punctuation">.</span><span class="z-source">Delay</span><span class="z-punctuation">,</span><span class="z-source"> delay</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation">.</span><span class="z-source">Image</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">anim</span><span class="z-punctuation">.</span><span class="z-source">Image</span><span class="z-punctuation">,</span><span class="z-source"> img</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> gif</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">EncodeAll</span><span class="z-punctuation">(</span><span class="z-source">out</span><span class="z-punctuation">,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-source">anim</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // NOTE: ignoring encoding errors</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_5#</span><span class="z-string"> ./a.out</span><span class="z-keyword z-operator"> &gt;</span><span class="z-string">out.gif</span></span></code></pre> <p><img src="/csdn/13_1.gif" alt="在这里插入图片描述" /></p> <h4 id="1-6">1.6</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.6: 修改Lissajous程序，修改其调色板来生成更丰富的颜色，</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 然后修改SetColorIndex的第三个参数，看看显示结果吧。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Lissajous generates GIF animations of random Lissajous figures.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image/color&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image/gif&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;math&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;math/rand&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;time&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">var palette </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> []</span><span class="z-source">color.Color</span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">White</span><span class="z-punctuation">,</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">Black</span><span class="z-punctuation">,</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">11</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">22</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">33</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">},</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">aa</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">bb</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">cc</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">bb</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">},</span><span class="z-punctuation z-definition z-comment z-comment"> // 红</span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">},</span><span class="z-punctuation z-definition z-comment z-comment"> // 绿</span></span> <span class="giallo-l"><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">},</span><span class="z-punctuation z-definition z-comment z-comment"> // 蓝</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-modifier">const</span><span class="z-punctuation"> (</span></span> <span class="giallo-l"><span class="z-source"> whiteIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation z-definition z-comment z-comment"> // first color in palette</span></span> <span class="giallo-l"><span class="z-source"> blackIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation z-definition z-comment z-comment"> // next color in palette</span></span> <span class="giallo-l"><span class="z-source"> color1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 2</span></span> <span class="giallo-l"><span class="z-source"> color2 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 3</span></span> <span class="giallo-l"><span class="z-source"> color3 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 4</span></span> <span class="giallo-l"><span class="z-source"> redIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"><span class="z-source"> greenIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 6</span></span> <span class="giallo-l"><span class="z-source"> blueIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 7</span></span> <span class="giallo-l"><span class="z-source"> colorNum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 8</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // The sequence of images is deterministic unless we seed</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // the pseudo-random number generator using the current time.</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // Thanks to Randall McPherson for pointing out the omission.</span></span> <span class="giallo-l"><span class="z-source"> rand</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Seed</span><span class="z-punctuation">(</span><span class="z-source">time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Now</span><span class="z-punctuation">().</span><span class="z-entity z-name z-function">UTC</span><span class="z-punctuation">().</span><span class="z-entity z-name z-function">UnixNano</span><span class="z-punctuation">())</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> lissajous</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stdout</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> lissajous</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">out io</span><span class="z-source">.</span><span class="z-variable z-parameter">Writer</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-modifier"> const</span><span class="z-punctuation"> (</span></span> <span class="giallo-l"><span class="z-source"> cycles </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 5</span><span class="z-punctuation z-definition z-comment z-comment"> // number of complete x oscillator revolutions</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.001</span><span class="z-punctuation z-definition z-comment z-comment"> // angular resolution</span></span> <span class="giallo-l"><span class="z-source"> size </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation z-definition z-comment z-comment"> // image canvas covers [-size..+size]</span></span> <span class="giallo-l"><span class="z-source"> nframes </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 64</span><span class="z-punctuation z-definition z-comment z-comment"> // number of animation frames</span></span> <span class="giallo-l"><span class="z-source"> delay </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 8</span><span class="z-punctuation z-definition z-comment z-comment"> // delay between frames in 10ms units</span></span> <span class="giallo-l"><span class="z-punctuation"> )</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> freq</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> rand</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Float64</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> *</span><span class="z-constant z-numeric"> 3.0</span><span class="z-punctuation z-definition z-comment z-comment"> // relative frequency of y oscillator</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> gif</span><span class="z-punctuation">.</span><span class="z-source">GIF</span><span class="z-punctuation">{</span><span class="z-source">LoopCount</span><span class="z-punctuation">:</span><span class="z-source"> nframes</span><span class="z-punctuation">}</span></span> <span class="giallo-l"><span class="z-source"> phase</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.0</span><span class="z-punctuation z-definition z-comment z-comment"> // phase difference</span></span> <span class="giallo-l"><span class="z-source"> colorIndex</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> uint8</span><span class="z-punctuation">(</span><span class="z-source">whiteIndex</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> i</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> nframes</span><span class="z-punctuation">;</span><span class="z-source"> i</span><span class="z-keyword z-operator">++</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> rect</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> image</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Rect</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 2</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 2</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> img</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> image</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">NewPaletted</span><span class="z-punctuation">(</span><span class="z-source">rect</span><span class="z-punctuation">,</span><span class="z-source"> palette</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> t</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.0</span><span class="z-punctuation">;</span><span class="z-source"> t </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> cycles</span><span class="z-keyword z-operator">*</span><span class="z-constant z-numeric">2</span><span class="z-keyword z-operator">*</span><span class="z-source">math</span><span class="z-punctuation">.</span><span class="z-source">Pi</span><span class="z-punctuation">;</span><span class="z-source"> t </span><span class="z-keyword z-operator">+=</span><span class="z-source"> res </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> x</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> math</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Sin</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> y</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> math</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Sin</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-keyword z-operator">*</span><span class="z-source">freq </span><span class="z-keyword z-operator">+</span><span class="z-source"> phase</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> img</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">SetColorIndex</span><span class="z-punctuation">(</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-storage z-type">int</span><span class="z-punctuation">(</span><span class="z-source">x</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">0.5</span><span class="z-punctuation">),</span><span class="z-source"> size</span><span class="z-keyword z-operator">+</span><span class="z-storage z-type">int</span><span class="z-punctuation">(</span><span class="z-source">y</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">0.5</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> colorIndex</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> colorIndex </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> uint8</span><span class="z-punctuation">(</span><span class="z-source">i </span><span class="z-keyword z-operator">%</span><span class="z-source"> colorNum</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 动态更新颜色</span></span> <span class="giallo-l"><span class="z-source"> phase </span><span class="z-keyword z-operator">+=</span><span class="z-constant z-numeric"> 0.1</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation">.</span><span class="z-source">Delay</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">anim</span><span class="z-punctuation">.</span><span class="z-source">Delay</span><span class="z-punctuation">,</span><span class="z-source"> delay</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation">.</span><span class="z-source">Image</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">anim</span><span class="z-punctuation">.</span><span class="z-source">Image</span><span class="z-punctuation">,</span><span class="z-source"> img</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> gif</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">EncodeAll</span><span class="z-punctuation">(</span><span class="z-source">out</span><span class="z-punctuation">,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-source">anim</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // NOTE: ignoring encoding errors</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_6#</span><span class="z-string"> ./a.out</span><span class="z-keyword z-operator"> &gt;</span><span class="z-string"> out.gif</span></span></code></pre> <p><img src="/csdn/13_2.gif" alt="在这里插入图片描述" /></p> <h4 id="1-7">1.7</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.7： 函数调用io.Copy(dst, src)会从src中读取内容，并将读到的结果</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 写入到dst中，使用这个函数替代掉例子中的ioutil.ReadAll来拷贝响应结构体到</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// os.Stdout，避免申请一个缓冲区（例子中的b）来存储。记得处理io.Copy返回结</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 果中的错误。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Fetch prints the content found at a URL.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;net/http&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 网络</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-source">:</span><span class="z-punctuation">] {</span></span> <span class="giallo-l"><span class="z-source"> resp</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Get</span><span class="z-punctuation">(</span><span class="z-source">url</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;fetch: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Exit</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // b, err := io.ReadAll(resp.Body)</span></span> <span class="giallo-l"><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> err </span><span class="z-keyword z-operator">=</span><span class="z-source"> io</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Copy</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stdout</span><span class="z-punctuation">,</span><span class="z-source"> resp</span><span class="z-punctuation">.</span><span class="z-source">Body</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 拷贝数据到标准输出</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;fetch: reading %s: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Exit</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> resp</span><span class="z-punctuation">.</span><span class="z-source">Body</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Close</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_7#</span><span class="z-string"> ./a.out https://www.baidu.com</span></span> <span class="giallo-l"><span class="z-keyword z-operator">&lt;!</span><span class="z-entity z-name z-function">DOCTYPE</span><span class="z-string"> htm</span><span class="z-source">l</span><span class="z-keyword z-operator">&gt;</span></span> <span class="giallo-l"><span class="z-keyword z-operator">&lt;!</span><span class="z-entity z-name z-function">--STATUS</span><span class="z-string"> OK-</span><span class="z-source">-&gt;&lt;</span><span class="z-string">htm</span><span class="z-source">l</span><span class="z-keyword z-operator">&gt; &lt;</span><span class="z-string">hea</span><span class="z-source">d&gt;&lt;</span><span class="z-string">meta http-equiv=content-type content=text/html</span><span class="z-punctuation">;</span><span class="z-source">charset</span><span class="z-keyword z-operator">=</span><span class="z-string">utf-8</span><span class="z-source">&gt;&lt;</span><span class="z-string">meta</span><span class="z-source"> http-equiv</span><span class="z-keyword z-operator">=</span><span class="z-string">X-UA-Compatible</span><span class="z-source"> content</span><span class="z-keyword z-operator">=</span><span class="z-source">IE</span><span class="z-keyword z-operator">=</span><span class="z-string">Edge</span><span class="z-source">&gt;&lt;</span><span class="z-string">meta</span><span class="z-source"> content</span><span class="z-keyword z-operator">=</span><span class="z-string">always</span><span class="z-source"> name</span><span class="z-keyword z-operator">=</span><span class="z-string">referrer</span><span class="z-source">&gt;&lt;</span><span class="z-string">link</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-support z-function z-builtin">...</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_7#</span><span class="z-source"> </span></span></code></pre><h4 id="1-8">1.8</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.8: 修改fetch这个范例，如果输入的url参数没有 http:// 前缀的话，</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 为这个url加上该前缀。你可能会用到strings.HasPrefix这个函数。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Fetch prints the content found at a URL.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;strings&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;net/http&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-source">:</span><span class="z-punctuation">] {</span></span> <span class="giallo-l"><span class="z-source"> prefix</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-punctuation z-definition z-string z-string"> &quot;https://&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 定义http前缀</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-keyword z-operator"> !</span><span class="z-source">strings</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">HasPrefix</span><span class="z-punctuation">(</span><span class="z-source">url</span><span class="z-punctuation">,</span><span class="z-source"> prefix</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否存在http前缀</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;No prefix, add &quot;</span><span class="z-punctuation">,</span><span class="z-source"> prefix</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> url </span><span class="z-keyword z-operator">=</span><span class="z-source"> prefix </span><span class="z-keyword z-operator">+</span><span class="z-source"> url</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 不是则添加上http前缀</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> resp</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Get</span><span class="z-punctuation">(</span><span class="z-source">url</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 请求访问，获取响应报文</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;fetch: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Exit</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> b</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> io</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">ReadAll</span><span class="z-punctuation">(</span><span class="z-source">resp</span><span class="z-punctuation">.</span><span class="z-source">Body</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 读取响应报文</span></span> <span class="giallo-l"><span class="z-source"> resp</span><span class="z-punctuation">.</span><span class="z-source">Body</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Close</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;fetch: reading %s: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Exit</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%s&quot;</span><span class="z-punctuation">,</span><span class="z-source"> b</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_8#</span><span class="z-string"> ./a.out www.baidu.com</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">No</span><span class="z-string"> prefix, add https://</span></span> <span class="giallo-l"><span class="z-keyword z-operator">&lt;!</span><span class="z-entity z-name z-function">DOCTYPE</span><span class="z-string"> htm</span><span class="z-source">l</span><span class="z-keyword z-operator">&gt;</span></span> <span class="giallo-l"><span class="z-keyword z-operator">&lt;!</span><span class="z-entity z-name z-function">--STATUS</span><span class="z-string"> OK-</span><span class="z-source">-&gt;&lt;</span><span class="z-string">htm</span><span class="z-source">l</span><span class="z-keyword z-operator">&gt; &lt;</span><span class="z-string">hea</span><span class="z-source">d&gt;&lt;</span><span class="z-string">meta http-equiv=content-type content=text/html</span><span class="z-punctuation">;</span><span class="z-source">charset</span><span class="z-keyword z-operator">=</span><span class="z-string">utf-8</span><span class="z-source">&gt;&lt;</span><span class="z-string">meta</span><span class="z-source"> http-equiv</span><span class="z-keyword z-operator">=</span><span class="z-string">X-UA-Compatible</span><span class="z-source"> content</span><span class="z-keyword z-operator">=</span><span class="z-source">IE</span><span class="z-keyword z-operator">=</span><span class="z-string">Edge</span><span class="z-source">&gt;&lt;</span><span class="z-string">meta</span><span class="z-source"> content</span><span class="z-keyword z-operator">=</span><span class="z-string">always</span><span class="z-source"> name</span><span class="z-keyword z-operator">=</span><span class="z-string">referrer</span><span class="z-source">&gt;&lt;</span><span class="z-string">link</span><span class="z-source"> rel</span><span class="z-keyword z-operator">=</span><span class="z-string">stylesheet</span><span class="z-source"> type</span><span class="z-keyword z-operator">=</span><span class="z-string">text/css</span><span class="z-source"> href</span><span class="z-keyword z-operator">=</span><span class="z-string">https://ss1.bdstatic.com/5eN1bjq8AAUYm2zgoY3K/r/www/cache/bdorz/baidu.min.css</span><span class="z-source">&gt;&lt;</span><span class="z-string">title</span><span class="z-keyword z-operator">&gt;</span><span class="z-string">百度一下，你就知道</span><span class="z-keyword z-operator">&lt;</span><span class="z-string">/title</span><span class="z-source">&gt;&lt;</span><span class="z-string">/head</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> &lt;body link=#0000cc&gt; &lt;div id=wrapper&gt; &lt;div id=head&gt; &lt;div class=head_wrapper&gt; &lt;div class=s_form&gt; &lt;div class=s_form_wrapper&gt; &lt;div id=lg&gt; &lt;img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129&gt; &lt;/div&gt; &lt;form id=form name=f action=//www.baidu.com/s class=fm&gt; &lt;input type=hidden name=bdorz_come value=1&gt; &lt;input type=hidden name=ie value=utf-8&gt; &lt;input </span></span> <span class="giallo-l"><span class="z-support z-function z-builtin">...</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_8#</span><span class="z-source"> </span></span></code></pre><h4 id="1-9">1.9</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.9: 修改fetch打印出HTTP协议的状态码，可以从resp.Status变量得到该状态码。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Fetch prints the content found at a URL.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;net/http&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-source">:</span><span class="z-punctuation">] {</span></span> <span class="giallo-l"><span class="z-source"> resp</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Get</span><span class="z-punctuation">(</span><span class="z-source">url</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;fetch: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Exit</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> b</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> io</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">ReadAll</span><span class="z-punctuation">(</span><span class="z-source">resp</span><span class="z-punctuation">.</span><span class="z-source">Body</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> resp</span><span class="z-punctuation">.</span><span class="z-source">Body</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Close</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-source"> err </span><span class="z-keyword z-operator">!=</span><span class="z-source"> nil </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">os</span><span class="z-punctuation">.</span><span class="z-source">Stderr</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;fetch: reading %s: %v</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation">,</span><span class="z-source"> err</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> os</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Exit</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%s&quot;</span><span class="z-punctuation">,</span><span class="z-source"> b</span><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> status</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> resp</span><span class="z-punctuation">.</span><span class="z-source">Status</span><span class="z-punctuation z-definition z-comment z-comment"> // 获取状态码</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;Status: &quot;</span><span class="z-punctuation">,</span><span class="z-source"> status</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 打印状态码</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_9#</span><span class="z-string"> ./a.out https://www.baidu.com</span></span> <span class="giallo-l"><span class="z-keyword z-operator">&lt;!</span><span class="z-entity z-name z-function">DOCTYPE</span><span class="z-string"> htm</span><span class="z-source">l</span><span class="z-keyword z-operator">&gt;</span></span> <span class="giallo-l"><span class="z-keyword z-operator">&lt;!</span><span class="z-entity z-name z-function">--STATUS</span><span class="z-string"> OK-</span><span class="z-source">-&gt;&lt;</span><span class="z-string">htm</span><span class="z-source">l</span><span class="z-keyword z-operator">&gt; &lt;</span><span class="z-string">hea</span><span class="z-source">d&gt;&lt;</span><span class="z-string">meta http-equiv=content-type content=text/html</span><span class="z-punctuation">;</span><span class="z-source">charset</span><span class="z-keyword z-operator">=</span><span class="z-string">utf-8</span><span class="z-source">&gt;&lt;</span><span class="z-string">meta</span><span class="z-source"> http-equiv</span><span class="z-keyword z-operator">=</span><span class="z-string">X-UA-Compatible</span><span class="z-source"> content</span><span class="z-keyword z-operator">=</span><span class="z-source">IE</span><span class="z-keyword z-operator">=</span><span class="z-string">Edge</span><span class="z-source">&gt;&lt;</span><span class="z-string">meta</span><span class="z-source"> content</span><span class="z-keyword z-operator">=</span><span class="z-string">always</span><span class="z-source"> name</span><span class="z-keyword z-operator">=</span><span class="z-string">referrer</span><span class="z-source">&gt;&lt;</span><span class="z-string">link</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-support z-function z-builtin">...</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Status:</span><span class="z-constant z-numeric"> 200</span><span class="z-string"> OK</span></span> <span class="giallo-l"><span class="z-source"> </span></span></code></pre><h4 id="1-10">1.10</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.10： 找一个数据量比较大的网站，用本小节中的程序调研网站的缓存</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 策略，对每个URL执行两遍请求，查看两次时间是否有较大的差别，并且每次获</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 取到的响应内容是否一致，修改本节中的程序，将响应结果输出到文件，以便于</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 进行对比。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Fetchall fetches URLs in parallel and reports their times and sizes.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;net/http&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;os&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;time&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-source"> start</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Now</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-source"> ch</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> make</span><span class="z-punctuation">(</span><span class="z-source">chan string</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // 新键通道（用于在routine之间传输数据）</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> _</span><span class="z-punctuation">,</span><span class="z-source"> url</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-source">:</span><span class="z-punctuation">] {</span></span> <span class="giallo-l"><span class="z-source"> go</span><span class="z-entity z-name z-function"> fetch</span><span class="z-punctuation">(</span><span class="z-source">url</span><span class="z-punctuation">,</span><span class="z-source"> ch</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // start a goroutine</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> range os</span><span class="z-punctuation">.</span><span class="z-source">Args</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">1</span><span class="z-source">:</span><span class="z-punctuation">] {</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Println</span><span class="z-punctuation">(</span><span class="z-keyword z-operator">&lt;-</span><span class="z-source">ch</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // receive from channel ch</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Printf</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%.2fs elapsed</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> time</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Since</span><span class="z-punctuation">(</span><span class="z-source">start</span><span class="z-punctuation">).</span><span class="z-entity z-name z-function">Seconds</span><span class="z-punctuation">())</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> fetch</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">url</span><span class="z-variable z-parameter"> string</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> ch chan</span><span class="z-punctuation">&lt;</span><span class="z-keyword z-operator">-</span><span class="z-entity z-name z-type"> string</span><span class="z-source">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> start</span><span class="z-source"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> time.</span><span class="z-entity z-name z-type">Now</span><span class="z-source">()</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> resp</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> err</span><span class="z-source"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> http.</span><span class="z-entity z-name z-type">Get</span><span class="z-source">(</span><span class="z-entity z-name z-type">url</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-source"> if</span><span class="z-entity z-name z-type"> err</span><span class="z-keyword z-operator"> !=</span><span class="z-entity z-name z-type"> nil</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> ch</span><span class="z-punctuation"> &lt;</span><span class="z-keyword z-operator">-</span><span class="z-source"> fmt.</span><span class="z-entity z-name z-type">Sprint</span><span class="z-source">(</span><span class="z-entity z-name z-type">err</span><span class="z-source">)</span><span class="z-punctuation z-definition z-comment z-comment"> // send to channel ch</span></span> <span class="giallo-l"><span class="z-source"> return</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 创建新文件（以时间戳命名）</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> fileName</span><span class="z-source"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> fmt.</span><span class="z-entity z-name z-type">Sprintf</span><span class="z-source">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%v.txt&quot;</span><span class="z-punctuation">,</span><span class="z-source"> start.</span><span class="z-entity z-name z-type">Nanosecond</span><span class="z-source">())</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> file</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> err</span><span class="z-source"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> os.</span><span class="z-entity z-name z-type">Create</span><span class="z-source">(</span><span class="z-entity z-name z-type">fileName</span><span class="z-source">) </span></span> <span class="giallo-l"><span class="z-source"> if</span><span class="z-entity z-name z-type"> err</span><span class="z-keyword z-operator"> !=</span><span class="z-entity z-name z-type"> nil</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> ch</span><span class="z-punctuation"> &lt;</span><span class="z-keyword z-operator">-</span><span class="z-source"> fmt.</span><span class="z-entity z-name z-type">Sprint</span><span class="z-source">(</span><span class="z-entity z-name z-type">err</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-source"> return</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 将响应结果保存至文件中</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> nbytes</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> err</span><span class="z-source"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> io.</span><span class="z-entity z-name z-type">Copy</span><span class="z-source">(</span><span class="z-entity z-name z-type">file</span><span class="z-punctuation">,</span><span class="z-source"> resp.</span><span class="z-entity z-name z-type">Body</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-source"> resp.Body.</span><span class="z-entity z-name z-type">Close</span><span class="z-source">()</span><span class="z-punctuation z-definition z-comment z-comment"> // don&#39;t leak resources</span></span> <span class="giallo-l"><span class="z-source"> file.</span><span class="z-entity z-name z-type">Close</span><span class="z-source">()</span><span class="z-punctuation z-definition z-comment z-comment"> // 关闭文件</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> if</span><span class="z-entity z-name z-type"> err</span><span class="z-keyword z-operator"> !=</span><span class="z-entity z-name z-type"> nil</span><span class="z-source"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> ch</span><span class="z-punctuation"> &lt;</span><span class="z-keyword z-operator">-</span><span class="z-source"> fmt.</span><span class="z-entity z-name z-type">Sprintf</span><span class="z-source">(</span><span class="z-punctuation z-definition z-string z-string">&quot;while reading %s: %v&quot;</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> url</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> err</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-source"> return</span></span> <span class="giallo-l"><span class="z-source"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> secs</span><span class="z-source"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> time.</span><span class="z-entity z-name z-type">Since</span><span class="z-source">(</span><span class="z-entity z-name z-type">start</span><span class="z-source">).</span><span class="z-entity z-name z-type">Seconds</span><span class="z-source">()</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> ch</span><span class="z-punctuation"> &lt;</span><span class="z-keyword z-operator">-</span><span class="z-source"> fmt.</span><span class="z-entity z-name z-type">Sprintf</span><span class="z-source">(</span><span class="z-punctuation z-definition z-string z-string">&quot;%.2fs %7d %s&quot;</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> secs</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> nbytes</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> url</span><span class="z-source">)</span></span> <span class="giallo-l"><span class="z-source">}</span></span> <span class="giallo-l"></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_10#</span><span class="z-string"> go build -o a.out</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_10#</span><span class="z-string"> ./a.out https://www.baidu.com https://www.baidu.com</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0.08s</span><span class="z-constant z-numeric"> 2443</span><span class="z-string"> https://www.baidu.com</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0.08s</span><span class="z-constant z-numeric"> 2443</span><span class="z-string"> https://www.baidu.com</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0.08s</span><span class="z-string"> elapsed</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_10#</span><span class="z-string"> ls</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">708404000.txt</span><span class="z-string"> 708408000.txt a.out main.go</span></span></code></pre><h4 id="1-11">1.11</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.11： 在fetchall中尝试使用长一些的参数列表，比如使用在alexa.com的上百万网站里排名靠前的。</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 如果一个网站没有回应，程序将采取怎样的行为？（Section8.9 描述了在这种情况下的应对机制）。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 答：没有回应程序会一直等待。</span></span></code></pre><h4 id="1-12">1.12</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 练习 1.12: 修改Lissajour服务，从URL读取变量，比如你可以访问 http://localhost:8000/?cycles=20 </span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 这个URL，这样访问可以将程序里的cycles默认的5修改为20。字符串转换为数字可以调用strconv.Atoi函数。你</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// 可以在godoc里查看</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// Server2 is a minimal &quot;echo&quot; and counter server.</span></span> <span class="giallo-l"><span class="z-source">package main</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">import </span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;fmt&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;log&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;net/http&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;sync&quot;</span><span class="z-punctuation z-definition z-comment z-comment"> // 同步</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;io&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;math/rand&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image/color&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;image/gif&quot;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-string z-string"> &quot;math&quot;</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">var mu sync</span><span class="z-punctuation">.</span><span class="z-source">Mutex</span></span> <span class="giallo-l"><span class="z-source">var count</span><span class="z-storage z-type"> int</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source">var palette </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> []</span><span class="z-source">color.Color</span><span class="z-punctuation">{</span><span class="z-source">color</span><span class="z-punctuation">.</span><span class="z-source">White</span><span class="z-punctuation">,</span><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">Black</span><span class="z-punctuation">,</span><span class="z-source"> color</span><span class="z-punctuation">.</span><span class="z-source">RGBA</span><span class="z-punctuation">{</span><span class="z-keyword">0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">00</span><span class="z-punctuation">,</span><span class="z-keyword"> 0x</span><span class="z-constant z-numeric">ff</span><span class="z-punctuation">}}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-modifier">const</span><span class="z-punctuation"> (</span></span> <span class="giallo-l"><span class="z-source"> whiteIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation z-definition z-comment z-comment"> // first color in palette</span></span> <span class="giallo-l"><span class="z-source"> blackIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation z-definition z-comment z-comment"> // next color in palette</span></span> <span class="giallo-l"><span class="z-source"> greenIndex </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation z-definition z-comment z-comment"> // 绿色</span></span> <span class="giallo-l"><span class="z-punctuation">)</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">() {</span></span> <span class="giallo-l"><span class="z-source"> http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">HandleFunc</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;/&quot;</span><span class="z-punctuation">,</span><span class="z-source"> handler</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">HandleFunc</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;/count&quot;</span><span class="z-punctuation">,</span><span class="z-source"> counter</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">HandleFunc</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;/lissajous&quot;</span><span class="z-punctuation">,</span><span class="z-entity z-name z-function"> func</span><span class="z-punctuation">(</span><span class="z-source">w http</span><span class="z-punctuation">.</span><span class="z-source">ResponseWriter</span><span class="z-punctuation">,</span><span class="z-source"> r </span><span class="z-keyword z-operator">*</span><span class="z-source">http</span><span class="z-punctuation">.</span><span class="z-source">Request</span><span class="z-punctuation">)</span><span class="z-source"> {</span><span class="z-punctuation z-definition z-comment z-comment"> // 添加lissajous访问接口</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> lissajous</span><span class="z-punctuation">(</span><span class="z-source">w</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> }</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> log</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fatal</span><span class="z-punctuation">(</span><span class="z-source">http</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">ListenAndServe</span><span class="z-punctuation">(</span><span class="z-punctuation z-definition z-string z-string">&quot;localhost:8000&quot;</span><span class="z-punctuation">,</span><span class="z-source"> nil</span><span class="z-punctuation">))</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// handler echoes the Path component of the requested URL.</span></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> handler</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">w http</span><span class="z-source">.</span><span class="z-variable z-parameter">ResponseWriter</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> r</span><span class="z-storage z-modifier"> *</span><span class="z-entity z-name z-type">http</span><span class="z-source">.</span><span class="z-variable z-parameter">Request</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> mu</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Lock</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-source"> count</span><span class="z-keyword z-operator">++</span></span> <span class="giallo-l"><span class="z-source"> mu</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Unlock</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">w</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;URL.Path = %q</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> r</span><span class="z-punctuation">.</span><span class="z-source">URL</span><span class="z-punctuation">.</span><span class="z-source">Path</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// counter echoes the number of calls so far.</span></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> counter</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">w http</span><span class="z-source">.</span><span class="z-variable z-parameter">ResponseWriter</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> r</span><span class="z-storage z-modifier"> *</span><span class="z-entity z-name z-type">http</span><span class="z-source">.</span><span class="z-variable z-parameter">Request</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> mu</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Lock</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-source"> fmt</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Fprintf</span><span class="z-punctuation">(</span><span class="z-source">w</span><span class="z-punctuation">,</span><span class="z-punctuation z-definition z-string z-string"> &quot;Count %d</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">,</span><span class="z-source"> count</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> mu</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Unlock</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-type">func</span><span class="z-entity z-name z-function"> lissajous</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">out io</span><span class="z-source">.</span><span class="z-variable z-parameter">Writer</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-modifier"> const</span><span class="z-punctuation"> (</span></span> <span class="giallo-l"><span class="z-source"> cycles </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 5</span><span class="z-punctuation z-definition z-comment z-comment"> // number of complete x oscillator revolutions</span></span> <span class="giallo-l"><span class="z-source"> res </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.001</span><span class="z-punctuation z-definition z-comment z-comment"> // angular resolution</span></span> <span class="giallo-l"><span class="z-source"> size </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation z-definition z-comment z-comment"> // image canvas covers [-size..+size]</span></span> <span class="giallo-l"><span class="z-source"> nframes </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 64</span><span class="z-punctuation z-definition z-comment z-comment"> // number of animation frames</span></span> <span class="giallo-l"><span class="z-source"> delay </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 8</span><span class="z-punctuation z-definition z-comment z-comment"> // delay between frames in 10ms units</span></span> <span class="giallo-l"><span class="z-punctuation"> )</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-source"> freq</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> rand</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Float64</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> *</span><span class="z-constant z-numeric"> 3.0</span><span class="z-punctuation z-definition z-comment z-comment"> // relative frequency of y oscillator</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> gif</span><span class="z-punctuation">.</span><span class="z-source">GIF</span><span class="z-punctuation">{</span><span class="z-source">LoopCount</span><span class="z-punctuation">:</span><span class="z-source"> nframes</span><span class="z-punctuation">}</span></span> <span class="giallo-l"><span class="z-source"> phase</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.0</span><span class="z-punctuation z-definition z-comment z-comment"> // phase difference</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> i</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> nframes</span><span class="z-punctuation">;</span><span class="z-source"> i</span><span class="z-keyword z-operator">++</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> rect</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> image</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Rect</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 2</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 2</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> img</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> image</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">NewPaletted</span><span class="z-punctuation">(</span><span class="z-source">rect</span><span class="z-punctuation">,</span><span class="z-source"> palette</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-source"> t</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0.0</span><span class="z-punctuation">;</span><span class="z-source"> t </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> cycles</span><span class="z-keyword z-operator">*</span><span class="z-constant z-numeric">2</span><span class="z-keyword z-operator">*</span><span class="z-source">math</span><span class="z-punctuation">.</span><span class="z-source">Pi</span><span class="z-punctuation">;</span><span class="z-source"> t </span><span class="z-keyword z-operator">+=</span><span class="z-source"> res </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> x</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> math</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Sin</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> y</span><span class="z-punctuation"> :</span><span class="z-keyword z-operator">=</span><span class="z-source"> math</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">Sin</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-keyword z-operator">*</span><span class="z-source">freq </span><span class="z-keyword z-operator">+</span><span class="z-source"> phase</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> img</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">SetColorIndex</span><span class="z-punctuation">(</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-storage z-type">int</span><span class="z-punctuation">(</span><span class="z-source">x</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">0.5</span><span class="z-punctuation">),</span><span class="z-source"> size</span><span class="z-keyword z-operator">+</span><span class="z-storage z-type">int</span><span class="z-punctuation">(</span><span class="z-source">y</span><span class="z-keyword z-operator">*</span><span class="z-source">size</span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric">0.5</span><span class="z-punctuation">),</span></span> <span class="giallo-l"><span class="z-source"> blackIndex</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> phase </span><span class="z-keyword z-operator">+=</span><span class="z-constant z-numeric"> 0.1</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation">.</span><span class="z-source">Delay</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">anim</span><span class="z-punctuation">.</span><span class="z-source">Delay</span><span class="z-punctuation">,</span><span class="z-source"> delay</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> anim</span><span class="z-punctuation">.</span><span class="z-source">Image</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> append</span><span class="z-punctuation">(</span><span class="z-source">anim</span><span class="z-punctuation">.</span><span class="z-source">Image</span><span class="z-punctuation">,</span><span class="z-source"> img</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> gif</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">EncodeAll</span><span class="z-punctuation">(</span><span class="z-source">out</span><span class="z-punctuation">,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-source">anim</span><span class="z-punctuation">)</span><span class="z-punctuation z-definition z-comment z-comment"> // NOTE: ignoring encoding errors</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">sy1_12#</span><span class="z-string"> go build -o a.out</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sy1_12#</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span></code></pre> <p><img src="/csdn/13_3.png" alt="" /></p> <h3 id="zong-jie">总结</h3> <ul> <li>Go语言是一门现代化的语言，从其方便的工具链、简洁的语法规则可得一瞥。</li> </ul> 2024-11-26T00:00:00+00:00 2024-11-26T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/12-valid-anagram/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定两个字符串 <code>s</code> 和 <code>t</code> ，编写一个函数来判断 <code>t</code> 是否是 <code>s</code> 的字母异位词。字母异位词是指通过重新排列不同单词或短语的字母而形成的单词或短语，并使用所有原字母一次。</p> <p>原题链接： <a rel="external" href="https://leetcode.cn/problems/valid-anagram/">242. 有效的字母异位词</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-pai-xu-fa">1 排序法</h3> <h4 id="fen-xi">分析</h4> <p>按照字母异位词的定义可知：如果两个字符串属于字母异位词，那么将两者排序后，其字符串必相同。</p> <h4 id="dai-ma">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> bool</span><span class="z-entity z-name z-function"> isAnagram</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> string</span><span class="z-variable z-parameter"> t</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> sort</span><span class="z-punctuation">(</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span><span class="z-punctuation z-definition z-comment z-comment"> // 排序s</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> sort</span><span class="z-punctuation">(</span><span class="z-source">t</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> t</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span><span class="z-punctuation z-definition z-comment z-comment"> // 排序t</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> s </span><span class="z-keyword z-operator">==</span><span class="z-source"> t</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 比较s和t是否相等</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(nlogn)</code> ，即快速排序长度为 <code>n</code> 的字符串的时间复杂度。</p> </li> <li> <p>空间复杂度： <code>O(logn)</code> ，即快速排序长度为 <code>n</code> 的字符串的空间复杂度。</p> </li> </ul> <h3 id="2ha-xi-biao">2哈希表</h3> <h4 id="fen-xi-1">分析</h4> <p>对比字符串中每个字母的使用次数，同样可以判断二者是否是字母异位词。正好可以字母为键、使用次数为值的哈希表作为数据结构。</p> <p>因为字母仅有 <code>26</code> 个小写字母组成，不妨将其映射到数值 <code>0～25</code> ，这样的话可直接使用数组存储哈希表。</p> <h4 id="dai-ma-1">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> bool</span><span class="z-entity z-name z-function"> isAnagram</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> string</span><span class="z-variable z-parameter"> t</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> sLen </span><span class="z-keyword z-operator">=</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 获取字符串s的长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tLen </span><span class="z-keyword z-operator">=</span><span class="z-source"> t</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 获取字符串t的长度</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">sLen </span><span class="z-keyword z-operator">!=</span><span class="z-source"> tLen</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果两者长度不一致</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 直接返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> table</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">26</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> {</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">};</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化哈希表为0</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> sLen</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历字符串s</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> -</span><span class="z-punctuation z-definition z-string z-string"> &#39;a&#39;</span><span class="z-punctuation">];</span><span class="z-punctuation z-definition z-comment z-comment"> // 构建哈希表</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> tLen</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历字符串t</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-keyword z-operator">--</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">t</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> -</span><span class="z-punctuation z-definition z-string z-string"> &#39;a&#39;</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> &lt;</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // “析构”哈希表，且如果发现计数小于0（说明字母出现次数不匹配）</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-true"> true</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回true</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du-1">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(n)</code> ，遍历长度为 <code>n</code> 的字符串.</p> </li> <li> <p>空间复杂度： <code>O(26)</code> ， <code>26</code> 个小写字母</p> </li> </ul> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li>使用特定字作为键的哈希表可以转换为用数组存储。</li> </ul> <hr /> 2024-11-19T00:00:00+00:00 2024-11-19T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/11-ransom-note/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定两个字符串： <code>ransomNote</code> 和 <code>magazine</code> ，判断 <code>ransomNote</code> 能不能由 <code>magazine</code> 里面的字符构成。其中 <code>magazine</code> 中的每个字符只能在 <code>ransomNote</code> 中使用一次，且 <code>ransomNote</code> 和 <code>magazine</code> 均由小写字母组成。</p> <p>原题链接： <a rel="external" href="https://leetcode.cn/problems/ransom-note/">383. 赎金信</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1ha-xi-biao">1哈希表</h3> <h4 id="fen-xi">分析</h4> <p>判断字符串ransomNote是否能由另一字符串magazine中的元素构成，只需要满足字符串magazine中每个元素的次数都大于等于ransomNote中相同元素的统计次数即可。所以该问题的关键是统计字符串所包含的全部元素以及元素的出现次数，并以一种合理的方式存储它们。</p> <p>已知元素只有小写字母组成，次数可以直接用整数表示，使用以字符为键、整形为值的哈希表存储，不管是构建还是使用都十分方便。</p> <p>易知：字符串ransomNote的必须小于字符串magazine的长度。</p> <h4 id="dai-ma">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> bool</span><span class="z-entity z-name z-function"> canConstruct</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> ransomNote</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> string</span><span class="z-variable z-parameter"> magazine</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> ransomNote</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">(),</span><span class="z-source"> m </span><span class="z-keyword z-operator">=</span><span class="z-source"> magazine</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 获取字符串长度</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">n </span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> m</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // ransomNote长度大于magazine长度</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 不满足条件，直接返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> unordered_map</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">char</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-keyword z-operator">&gt;</span><span class="z-entity z-name z-function"> table</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">);</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化哈希表为零（零表示该字符不存在）</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> m</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历magazine，构建哈希表</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">magazine</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)];</span><span class="z-punctuation z-definition z-comment z-comment"> // 该元素对应次数累加</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历ransomNote字符串</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-keyword z-operator">--</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">ransomNote</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)]</span><span class="z-keyword z-operator"> &lt;</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 出现一次字符，对应哈希表减一</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 出现小于0（代表字符不够），直接返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-true"> true</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回true</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(m+n)</code> ，即两个字符串的长度和</p> </li> <li> <p>空间复杂度： <code>O(26)</code> ，即 <code>26</code> 个小写英文字符</p> </li> </ul> <h3 id="2shu-zu-ha-xi-biao">2数组哈希表</h3> <h4 id="fen-xi-1">分析</h4> <p>已知哈希表中键只由 <code>26</code> 个小写英文字母 <code>a~z</code> 组成，易将其映射到 <code>0~25</code> ，因此可以用数组作为哈希表的实现方式。</p> <h4 id="dai-ma-1">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> bool</span><span class="z-entity z-name z-function"> canConstruct</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> ransomNote</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> string</span><span class="z-variable z-parameter"> magazine</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> table</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">26</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> {</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">};</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化数组哈希表为0</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> ransomNote</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">(),</span><span class="z-source"> m </span><span class="z-keyword z-operator">=</span><span class="z-source"> magazine</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 获取两字符串长度</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">n </span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> m</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // ransomNote长度大于magazine长度</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 不满足条件，直接返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> m</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历magazine，构建数组哈希表</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">magazine</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> -</span><span class="z-punctuation z-definition z-string z-string"> &#39;a&#39;</span><span class="z-punctuation">];</span><span class="z-punctuation z-definition z-comment z-comment"> // 数组哈希表对应元素值加1</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历ransomNote</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-keyword z-operator">--</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">ransomNote</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> -</span><span class="z-punctuation z-definition z-string z-string"> &#39;a&#39;</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> &lt;</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 数组哈希表对应元素减1</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 出现小于0，直接返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-true"> true</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回true</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du-1">复杂度</h4> <p>同上</p> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li>哈希表并不一定要使用专门的数据结构，也可以用数组实现。</li> </ul> <hr /> 2024-11-12T00:00:00+00:00 2024-11-12T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/10-h-index/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定一个整数数组 <code>citations</code> ，其中 <code>citations[i]</code> 代表研究者的第 <code>i</code> 篇论文被引用的次数。计算并返回该研究者的 <code>h</code> 指数。</p> <p><code>h</code> 代表“高引用次数“，一名科研人员的 <code>h</code> 指数是指他（她）至少发表了 <code>h</code> 篇论文，且至少有 <code>h</code> 篇论文的被引用次数大于等于 <code>h</code> 。如果 <code>h</code> 有多种可能值，那 <code>h</code> 指数是其中最大的那个。</p> <p><a rel="external" href="https://leetcode.cn/problems/h-index/">274. H 指数</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-bao-li-fa">1 暴力法</h3> <h4 id="fen-xi">分析</h4> <p>因为 <code>h</code> 指数一定小于等于论文数，因此只要穷举所有的论文数，就一定能找到 <code>h</code> 指数。</p> <p>具体做法如下：使用两层循环，第一层循环尝试所有可能的引用数（最大为论文数）作为 <code>h</code> 指数的候选值，第二层循环遍历数组，记录引用次数大于 <code>h</code> 的元素个数即论文数，找到最大满足「论文数大于引用数」的值，即为 <code>h</code> 值。</p> <h4 id="dai-ma">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> hIndex</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> citations</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 转储数组大小</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> refCnt </span><span class="z-keyword z-operator">=</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化最高引用数为数组大小（论文篇数）</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">refCnt</span><span class="z-keyword z-operator">--</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 尝试所有可能的引用次数（从高到低）</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> paperCnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化高引用论文数为0</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> j </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> j </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">j</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">citations</span><span class="z-punctuation">[</span><span class="z-source">j</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> &gt;=</span><span class="z-source"> refCnt</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 记录引用次数高于指定次数的论文</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">paperCnt</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">paperCnt </span><span class="z-keyword z-operator">&gt;=</span><span class="z-source"> refCnt</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果首次找到（即最高）满足条件引用次数，跳出循环</span></span> <span class="giallo-l"><span class="z-keyword"> break</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> refCnt</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回引用次数</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(n^2)</code> ，遍历长度为 <code>n</code> 的数组嵌套遍历两次。</p> </li> <li> <p>空间复杂度： <code>O(1)</code> ，只使用常数个变量。</p> </li> </ul> <h3 id="2-pai-xu">2 排序</h3> <h4 id="fen-xi-1">分析</h4> <p><code>h</code> 指数代表“高引用次数”，不妨将代表论文引用次数的数组 <code>citations</code> 排序。此时，只要找到一个位置的引用次数，大于其之后的元素个数（论文篇数），该引用次数即为 <code>h</code> 指数。</p> <p>因为需要计算数组中某一位置元素后的元素个数，反向遍历比较合适，具体做法如下：初始化一变量为0，用于存储元素个数，反向遍历数组，在每次访问完一元素时，累加该变量。</p> <h4 id="dai-ma-1">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> hIndex</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> citations</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> sort</span><span class="z-punctuation">(</span><span class="z-source">citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span><span class="z-punctuation z-definition z-comment z-comment"> // 排序</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 转储数组打下</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> h </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化h指数为0</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> --</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 反向遍历排序后的数组</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">citations</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> &gt;</span><span class="z-source"> h</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果引用次数大于h指数</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">h</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // h指数累加</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> h</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回h指数</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du-1">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(nlogn)</code> ，即排序长度为 <code>n</code> 数组的时间复杂度。</p> </li> <li> <p>空间复杂度： <code>O(n)</code> ，即排序长度为 <code>n</code> 数组的空间复杂度。</p> </li> </ul> <h3 id="3-ji-shu-pai-xu">3 计数排序</h3> <blockquote> <p>计数排序：将原数组以新的计数数组方式存储，以达到排序效果。其中计数数组是：数组下标为元素值，数组元素为原数组元素出现的次数。因为数组下标（此时还表示原数组元素）本就是排序好的，因此也可以看作是一种排序。新的数组大小也就是原数组中最大的值，因此计数排序一般用于整数数组，且最大值已知。</p> </blockquote> <h4 id="fen-xi-2">分析</h4> <p>计数排序的关键在于找到原数组的最大值，以方便构建计数数组。由题意知： <code>h</code> 指数不会大于研究者的论文篇数 <code>n</code> ，因此所有引用次数大于 <code>n</code> 的论文都可以存储在第 <code>n+1</code> 个位置。也就是说计数数组大小为 <code>n+1</code> 。</p> <p>当获得按计数排序的数组后，反向遍历，累加论文篇数（数组元素），找到首次论文篇数大于等于引用数（数组下标）的下标位置，此时的下标值即为 <code>h</code> 指数。</p> <h4 id="dai-ma-2">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> hIndex</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> citations</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 转储数组大小</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化计数和为0</span></span> <span class="giallo-l"><span class="z-source"> vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">int</span><span class="z-keyword z-operator">&gt;</span><span class="z-entity z-name z-function"> counter</span><span class="z-punctuation">(</span><span class="z-source">n </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">);</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化计数数组为{0}，用于存储按计数排序后的数组</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组，构建计数数组</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> &gt;</span><span class="z-source"> n</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 引用次数大于n，按照次数为n记录</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">counter</span><span class="z-punctuation">[</span><span class="z-source">n</span><span class="z-punctuation">];</span><span class="z-punctuation z-definition z-comment z-comment"> // </span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">counter</span><span class="z-punctuation">[</span><span class="z-source">citations</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">)];</span><span class="z-punctuation z-definition z-comment z-comment"> // 否则按照实际次数记录</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> --</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 反向遍历计数数组</span></span> <span class="giallo-l"><span class="z-source"> cnt </span><span class="z-keyword z-operator">+=</span><span class="z-source"> counter</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">i</span><span class="z-punctuation">);</span><span class="z-punctuation z-definition z-comment z-comment"> // 累加当前引用次数下的论文篇数</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">cnt </span><span class="z-keyword z-operator">&gt;=</span><span class="z-source"> i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 论文篇数大于等于当前引用次数</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> i</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 找到h指数，返回结果</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 为找到h指数，返回0</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du-2">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(n)</code> ，遍历数组长度为 <code>n</code> 的 <code>citations</code> 数组一次，遍历数组长度为 <code>n+1</code> 的 <code>counter</code> 数组一次。</p> </li> <li> <p>空间复杂度： <code>O(n)</code> ，构建长度为 <code>n+1</code> 的数组 <code>counter</code> 。</p> </li> </ul> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li>当排序能解决问题，且数组元素为整数值时，不妨考虑计数排序。</li> </ul> <hr /> 2024-11-11T00:00:00+00:00 2024-11-11T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/09-length-of-last-word/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定一个字符串 <code>s</code> ，由若干单词组成，单词前后有一些空格字符隔开。返回字符串中最后一个单词的长度。</p> <p><a rel="external" href="https://leetcode.cn/problems/length-of-last-word/">58. 最后一个单词的长度</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-ni-xu-bian-li">1 逆序遍历</h3> <h4 id="fen-xi">分析</h4> <p>初始化最后一个单词长度 <code>length = 0</code> ，逆序遍历数组，累加 <code>length</code> ，直到找到第一个为空格字符的元素。此时 <code>length</code> 即为所求值。值得注意的是：字符串末尾可能含有空格字符，需先清除它们，再开始计数单词长度。</p> <h4 id="dai-ma">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> lengthOfLastWord</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> length </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> start </span><span class="z-keyword z-operator">=</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化最后一个单词长度为0，逆序下标为n-1</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">start </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-keyword z-operator"> &amp;&amp;</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">start</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> ==</span><span class="z-punctuation z-definition z-string"> &#39; &#39;</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果存在末尾空格，清除它们（跳过）</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> --</span><span class="z-source">start</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新下标</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">start </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-keyword z-operator"> &amp;&amp;</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">at</span><span class="z-punctuation">(</span><span class="z-source">start</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> !=</span><span class="z-punctuation z-definition z-string"> &#39; &#39;</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 循环直到找到空格字符</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">length</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 单词长度+1</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> --</span><span class="z-source">start</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新下标</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> length</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回单词长度</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <ul> <li> <p>时间复杂度： <code>O(n)</code> ，遍历（逆序）长度为 <code>n</code> 的数组一次。</p> </li> <li> <p>空间复杂度： <code>O(1)</code> ，常数个变量。</p> </li> </ul> <h2 id="san-zong-jie">三 总结</h2> <ul> <li>正序遍历不好解决问题时，不妨考虑逆序遍历。</li> </ul> <hr /> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/01-majority-element/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>统计数组中出现次数大于「n/2」的元素，其中n为数组长度，你可以假设该类元素必存在。</p> <p>[ <a rel="external" href="https://leetcode.cn/problems/majority-element/">169. 多数元素</a> ]</p> <blockquote> <p>注意：「n/2」代表对算式 n/2 的结果向下取整，下同。</p> </blockquote> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1ha-xi-biao-fa">1哈希表法</h3> <h4 id="fen-xi">分析</h4> <p>题目要求统计出现次数大于「n/2」的元素，显而易见的方法是：统计所有元素出现的次数，找到其中大于「n/2」的元素。为了方便查找，使用以元素值为键、元素出现次数为值的哈希表作为数据结构。只要构建好哈希表后，目标元素就容易找出来了。</p> <h4 id="dai-ma">代码</h4> <ul> <li> <p>初始化以元素为键，以出现次数为值的哈希表</p> </li> <li> <p>遍历数组，将元素存放在哈希表中</p> </li> <li> <p>在遍历过程中，检查是否存在值大于「n/2」的元素，存在则返回该元素。</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> majorityElement</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> unordered_map</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> table</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> len </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> num </span><span class="z-keyword z-operator">=</span><span class="z-source"> len </span><span class="z-keyword z-operator">/</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation">,</span><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> len</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-keyword z-operator">++</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]]</span><span class="z-keyword z-operator"> &gt;</span><span class="z-source"> num</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-keyword"> break</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span></code></pre> <ul> <li>或者也可以在构建完成哈希表之后，遍历找到值最大的键（次数大于「n/2」肯定是最值），即为所需结果。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> majorityElement</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> unordered_map</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> table</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> len </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-storage z-type"> size_t</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> len</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">table</span><span class="z-punctuation">[</span><span class="z-source">nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]];</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-modifier z-storage z-type">const auto</span><span class="z-keyword z-operator">&amp;</span><span class="z-source"> item </span><span class="z-punctuation">:</span><span class="z-source"> table</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">item</span><span class="z-punctuation">.</span><span class="z-source">second</span><span class="z-keyword z-operator"> &gt;</span><span class="z-source"> cnt</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-source"> item</span><span class="z-punctuation">.</span><span class="z-source">second</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-source"> item</span><span class="z-punctuation">.</span><span class="z-source">first</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h3 id="2-pai-xu-fa">2 排序法</h3> <h4 id="fen-xi-1">分析</h4> <p>将数组排序，因为结果元素值出现次数大于「n/2」，考虑最极端情况：结果值最大/最小（起始/终止）且结果值次数为「n/2」+1，其数组下标「n/2」的位置也为该结果值，不管数组大小是奇数还是偶数。</p> <h4 id="dai-ma-1">代码</h4> <ul> <li> <p>给数组排序</p> </li> <li> <p>访问下标「n/2」位置的元素值</p> </li> </ul> <pre class="giallo z-code"><code data-lang="c"><span class="giallo-l"><span class="z-source">class Solution </span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source">public:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> majorityElement</span><span class="z-punctuation">(</span><span class="z-source">vector</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">int</span><span class="z-keyword z-operator">&gt;&amp;</span><span class="z-source"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> sort</span><span class="z-punctuation">(</span><span class="z-source">nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-source">nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> /</span><span class="z-constant z-numeric"> 2</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h2 id="san-zong-jie">三 总结</h2> <p>找到数据的特性，解决问题的方法也许很简单。比如方法2中提到排序法，是利用众数的特性，从而让我们可以快速找到目标元素。</p> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/02-best-time-to-buy-and-sell-stock/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定一个数组，找到两个元素，使得后一个元素减去前一个元素的值最大，返回这个最大值。如果不存在则返回0。</p> <p><a rel="external" href="https://leetcode.cn/problems/best-time-to-buy-and-sell-stock/">121.买卖股票的最佳时机</a></p> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-bao-li-fa">1 暴力法</h3> <h4 id="fen-xi">分析</h4> <p>因为需要找到两个元素，很容易想到遍历两次数组的暴力法：第一层循环记录前一个元素下标，第二层循环记录后一个元素下标，找到二者差的最大值。</p> <h4 id="dai-ma">代码</h4> <ul> <li> <p>第一次遍历数组，用 <code>i</code> 记录前一个元素下标</p> </li> <li> <p>第二次遍历数组，用 <code>j</code> 记录后一个元素下标，且 <code>j</code> 直接从 <code>i + 1</code> 开始</p> </li> <li> <p>二者相减，保存相减后的最大值</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> maxProfit</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> prices</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> nums </span><span class="z-keyword z-operator">=</span><span class="z-source"> prices</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 数组长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> cur</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回值（最大差值）和临时值</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> nums </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 第一层循环：记录前一个元素下标</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> j </span><span class="z-keyword z-operator">=</span><span class="z-source"> i </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-source"> j </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> nums</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">j</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 第二层循环：记录后一个元素下标</span></span> <span class="giallo-l"><span class="z-source"> cur </span><span class="z-keyword z-operator">=</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">j</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> -</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">];</span><span class="z-punctuation z-definition z-comment z-comment"> // 计算二者差值</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">cur </span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> ret</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 与最大差值比较</span></span> <span class="giallo-l"><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-source"> cur</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新最大差值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回结果</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre> <p>这里运用到了一个代码小技巧，因为最小值必为0（自己减自己），因此可令返回值默认为0，之后就可在两层循环中省去下标重复的地方。比如： <code>i &lt; nums - 1</code> 和 <code>j = i + 1</code> 。</p> <h3 id="2-wei-hu-zui-xiao-zhi">2 维护最小值</h3> <h4 id="fen-xi-1">分析</h4> <p>对于数组里任一元素来说，要想取得最大结果差值，其必须和出现在数组前面的最小值相减。因此可以维护一个最小值，用于跟当前数组元素比较。此时只用了一个循环。</p> <h4 id="dai-ma-1">代码</h4> <ul> <li> <p>记录首值为最小值，记录0为最大差值</p> </li> <li> <p>遍历数组除首值之外部分</p> </li> <li> <p>更新最大差值，更新最小值</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> maxProfit</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> prices</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> nums </span><span class="z-keyword z-operator">=</span><span class="z-source"> prices</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 数组长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> minPrice </span><span class="z-keyword z-operator">=</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">],</span><span class="z-source"> maxProfit </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 最小值，最大差值</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> nums</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组</span></span> <span class="giallo-l"><span class="z-source"> maxProfit </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-source">maxProfit</span><span class="z-punctuation">,</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> -</span><span class="z-source"> minPrice</span><span class="z-punctuation">);</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新最大差值</span></span> <span class="giallo-l"><span class="z-source"> minPrice </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> min</span><span class="z-punctuation">(</span><span class="z-source">prices</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">],</span><span class="z-source"> msnPrice</span><span class="z-punctuation">);</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新最小值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> maxProfit</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回结果值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h2 id="san-zong-jie">三 总结</h2> <ol> <li> <p>暴力法用了两层循环，所以时间复杂度为 $0(n^2)$ ；只用了常数个变量，所以空间复杂度为 $0(1)$ 。因为时间复杂度高，无法通过时间限制测试。</p> </li> <li> <p>维护最小值法只用了单层循环，时间复杂度为 $0(n)$ ；只用了常数个变量，所以空间复杂度也为 $0(1)$ 。</p> </li> <li> <p>维护最小值也可以看作双指针法的变体，其中仍有一个指针用于遍历数组，但另一个记录下标的指针则变成了记录元素值的变量。</p> </li> </ol> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/03-best-time-to-buy-and-sell-stock-ii/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定一个数组，查找数组中所有存在的元素对，使得元素对差值（后一个元素减去前一个的值）和最大。元素对之间不相交，求所有元素对的最大差值和。</p> <p><a rel="external" href="https://leetcode.cn/problems/best-time-to-buy-and-sell-stock-ii/">122. 买卖股票的最佳时机 II</a></p> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-tan-xin-fa">1 贪心法</h3> <h4 id="fen-xi">分析</h4> <p>直接找出所有最优元素对十分困难，不妨换种思路——找最小范围元素对。</p> <p>计算所有最小范围的元素对（即相邻元素，这是十分简单能找到的）的最优差值，累加这些差值即可得到最大差值和，所以关键是如何确保相邻元素差值最优。</p> <p>因为元素对可以只有一个元素，因此可以确保差值最小值必大于等于0，也就是说累加所有相邻元素的差值和0的较大者，即可获得最大差值和。</p> <h4 id="dai-ma">代码</h4> <ul> <li> <p>初始化最大差值和为0</p> </li> <li> <p>从第二个元素开始遍历数组</p> </li> <li> <p>比较相邻元素（当前元素值减去前面的元素值）和0的大小，将较大者累加入最大差值中去</p> </li> <li> <p>返回最大差值</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> maxProfit</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> prices</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> ret </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> len </span><span class="z-keyword z-operator">=</span><span class="z-source"> prices</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化最大差值和为0；记录数组大小（用于遍历）</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> len</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 从第二个元素开始循环（因为需要计算相邻元素差）</span></span> <span class="giallo-l"><span class="z-source"> ret </span><span class="z-keyword z-operator">+=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">,</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> -</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">i </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">]);</span><span class="z-punctuation z-definition z-comment z-comment"> // 将相邻元素差与0中对较大者累加入最大差值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> ret</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回最大差值和</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h3 id="2dong-tai-gui-hua">2动态规划</h3> <h4 id="fen-xi-1">分析</h4> <p>仍然考虑由局部最优推倒出全局最优。</p> <p>从数组的第一个元素开始，存在两种状态：一是可以将其作为元素对的起始、二是将其作为元素对的结束（后面将简记为起始状态和结束状态），同时记录两种状态下的解：起始状态解是0，终止状态解是当前元素值的负数（假定后面一定能找到一个元素与其组成元素对，因此解是负数）。</p> <p>对于下一个元素，其状态也可以是起始或结束，且只与前一个元素的状态有关，计算下一个元素解方法为：新状态结束解=max(旧状态结束解, 旧状态起始解 + 当前元素值)；新状态起始解=max(旧状态起始解, 旧状态结束解 - 当前元素值)，取max以确保局部最优。</p> <p>以此类推，直到运行至数组的最后一个元素，即可获得两种状态下各自的全局最优解（最大差值和）。</p> <p>因为最后为结束状态一定比起时状态差值和大，所以结果选结束状态更优。</p> <h4 id="dai-ma-1">代码</h4> <ul> <li> <p>初始化起始状态值和结束状态值</p> </li> <li> <p>遍历数组</p> </li> <li> <p>更新起始状态值和终止状态值</p> </li> <li> <p>返回最后元素结束状态下的值（最大差值和）</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> maxProfit</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> prices</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> prices</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 记录数组长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> dp0 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> dp1 </span><span class="z-keyword z-operator">= -</span><span class="z-source">prices</span><span class="z-punctuation">[</span><span class="z-constant z-numeric">0</span><span class="z-punctuation">];</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化两种状态的最大差值和，0为结束状态，1为起始状态</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> newDp0</span><span class="z-punctuation">,</span><span class="z-source"> newDp1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 临时变量，存放当前状态的最优解</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组</span></span> <span class="giallo-l"><span class="z-source"> newDp0 </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-source">dp0</span><span class="z-punctuation">,</span><span class="z-source"> dp1 </span><span class="z-keyword z-operator">+</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]);</span><span class="z-punctuation z-definition z-comment z-comment"> // 计算新结束状态值</span></span> <span class="giallo-l"><span class="z-source"> newDp1 </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-source">dp1</span><span class="z-punctuation">,</span><span class="z-source"> dp0 </span><span class="z-keyword z-operator">-</span><span class="z-source"> prices</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]);</span><span class="z-punctuation z-definition z-comment z-comment"> // 计算新起始状态值</span></span> <span class="giallo-l"><span class="z-source"> dp0 </span><span class="z-keyword z-operator">=</span><span class="z-source"> newDp0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新</span></span> <span class="giallo-l"><span class="z-source"> dp1 </span><span class="z-keyword z-operator">=</span><span class="z-source"> newDp1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> dp0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回最后元素结束状态下的值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li> <p>当局部最优能够推到出全局最优时，贪心算法是一种很好的思路方法。</p> </li> <li> <p>当程序出现多种状态，且状态前后相互影响时，可以尝试动态规划算法，其关键是找到状态和状态转变的方式。</p> </li> </ul> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/04-jump-game/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定一个非负整数数组 <code>nums</code> ，你最初位于数组的首个位置，每个元素值代表你在该位置可以跳跃的最大长度。判断是否能从首个位置跳到最后一个位置。</p> <p><a rel="external" href="https://leetcode.cn/problems/jump-game/">55. 跳跃游戏</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-tan-xin-fa">1 贪心法</h3> <h4 id="fen-xi">分析</h4> <p>对于数组内任意位置 <code>i</code> 的元素 <code>nums[i]</code> ，存在 <code>{i, i + 1, ... , i + nums[i]}</code> 个位置可以达。当跳跃到这些位置中的某一个的时候，在新的位置上又会产生一系列新的可达位置。也就是说，我们需要判断最后一个元素位置是否存在在这些位置、或这些位置的可达位置中。</p> <p>因为我们希望能达到的位置离数组最后一个位置越近越好，因此对于每一个位置的元素，我们都查找其最大的可达位置。如果所有的可达位置元素都不可达最后一个位置，那么数组也就无法从首个位置跳到最后一个位置。</p> <p>最初位于数组的首个位置，也就是说在最初的最远可达位置是 <code>0</code> 。</p> <h4 id="dai-ma">代码</h4> <ul> <li> <p>初始化可达最远位置为0</p> </li> <li> <p>遍历数组</p> </li> <li> <p>如果数组元素可达，更新最大可达位置</p> </li> <li> <p>检查是否可达数组最后一个位置</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> bool</span><span class="z-entity z-name z-function"> canJump</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 记录数组长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> maxIdx </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化可达最远位置为0</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">i </span><span class="z-keyword z-operator">&lt;=</span><span class="z-source"> maxIdx</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果元素可达（可跳跃）</span></span> <span class="giallo-l"><span class="z-source"> maxIdx </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-source">maxIdx</span><span class="z-punctuation">,</span><span class="z-source"> i </span><span class="z-keyword z-operator">+</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]);</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新最大可达位置</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">maxIdx </span><span class="z-keyword z-operator">&gt;=</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 如果可达数组最后一个位置</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-true"> true</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回true</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历完数组仍不可达最后一个位置，返回false</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre> <ul> <li>也可将条件 <code>i &lt; n</code> 和 <code>i &lt;= maxIdx</code> 合并，循环只遍历到可达的最大范围。</li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> bool</span><span class="z-entity z-name z-function"> canJump</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> maxIdx </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;=</span><span class="z-source"> maxIdx</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> maxIdx </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-source">maxIdx</span><span class="z-punctuation">,</span><span class="z-source"> i </span><span class="z-keyword z-operator">+</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]);</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">maxIdx </span><span class="z-keyword z-operator">&gt;=</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-true"> true</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-language z-false"> false</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre> <p>注意：如果可达的最大位置超过数组长度，那么将其作为下标访问数组，会出现数组越界的风险吗？</p> <p>不会，在代码中只要可跳跃的最大位置大于等于数组长度-1，就会跳出循环。</p> <hr /> <h2 id="san-zong-jie">三 总结</h2> <p>贪心算法是一种步步为营的策略，每一小步达到最优使得整体达到最优。</p> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/05-jump-game-ii/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定长度为 <code>n</code> 的整数数组 <code>nums</code> ，每个元素 <code>nums[i]</code> 代表从索引 <code>i</code> 向前跳跃的最大长度。初始位置为 <code>0</code> ，返回达到 <code>n-1</code> 的最小跳跃次数。（假定数组一定能跳到 <code>n-1</code> ）</p> <p><a rel="external" href="https://leetcode.cn/problems/jump-game-ii/">45.跳跃游戏 II</a></p> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-tan-xin-fa">1 贪心法</h3> <h4 id="fen-xi-1-fan-xiang">分析1—反向</h4> <p>直接从前往后找到最优的跳跃位置并计算出其所需花费的跳跃次数，并不是很容易（因为无法从判定当前最优位置的下一个位置仍是否最优）。但已知位置 <code>n-1</code> 必可达，不妨反过来试试从后往前找。</p> <p>假定已经有了第一层的从后往前遍历，那么此时如果第二层循环从前往后遍历，就能找到最优的能跳位置（能从该位置跳跃至当前位置）。因此此时位置越小越优，所以从前往后找到的第一个满足条件的位置即最优位置。</p> <p>之后，只需要每找到一个最优能跳位置，最小步数加1并跳出该层循环。</p> <h4 id="dai-ma-1">代码1</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> jump</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> pos </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 当前元素位置</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> minStep </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化最小步数为0</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">pos </span><span class="z-keyword z-operator">&gt;</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 反向遍历数组直到起始位置</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> pos</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 正向遍历找到最优跳跃位置</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">i </span><span class="z-keyword z-operator">+</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> &gt;=</span><span class="z-source"> pos</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 找到能达到当前位置的位置</span></span> <span class="giallo-l"><span class="z-source"> pos </span><span class="z-keyword z-operator">=</span><span class="z-source"> i</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新当前位置</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">minStep</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 累加步数</span></span> <span class="giallo-l"><span class="z-keyword"> break</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 跳出该层循环</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> minStep</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回最小步数</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fen-xi-2-zheng-xiang">分析2—正向</h4> <p>实际上，计算最小跳跃次数不需要找到最优的跳跃位置，而只要知道最优的可达范围，这可以通过比较现有数组的可达范围而获得。</p> <p>我们的做法是：从位置 <code>0</code> 开始从左往右遍历，记当前可达最大下标位置为一个临界值（作为完成跳跃一次的标志）。当前位置来到临界位置时，跳跃次数加1，直到遍历至最后位置 <code>n-1</code> 。</p> <p>又已知数组经过一定次数跳跃必能达到 <code>n-1</code> 位置，也就是说：在倒数第二次跳跃时，其位置必不在 <code>n-1</code> 位置（可以停下来想一想）。因此只需要遍历数组 <code>[0,n-1)</code> ，而不是 <code>[0,n)</code> 。</p> <h4 id="dai-ma-2">代码2</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> jump</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> nums</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 数组长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> minStep </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> maxPos </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> end </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化最小步数，最大下标位置和临界位置为0</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历数组[0,n-1)</span></span> <span class="giallo-l"><span class="z-source"> maxPos </span><span class="z-keyword z-operator">=</span><span class="z-entity z-name z-function"> max</span><span class="z-punctuation">(</span><span class="z-source">maxPos</span><span class="z-punctuation">,</span><span class="z-source"> i </span><span class="z-keyword z-operator">+</span><span class="z-source"> nums</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]);</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新当前最大可达范围</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">i </span><span class="z-keyword z-operator">==</span><span class="z-source"> end</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 判断是否达到临界位置</span></span> <span class="giallo-l"><span class="z-source"> end </span><span class="z-keyword z-operator">=</span><span class="z-source"> maxPos</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新临界值</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">minStep</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 累加最小步数</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> minStep</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回最小步数</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li> <p>当正向遍历不能解决问题的时候，不妨想想反向遍历。</p> </li> <li> <p>有时候信息不需要明确知道。如：本题中只需知道最小步数的每一步的最优范围，而不需知道每一步的具体位置。</p> </li> </ul> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/06-merge-sorted-array/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>给定两个非递减顺序的数组 <code>num1</code> 和 <code>nums2</code> ，和另两个表示其有效元素个数的整数 <code>m</code> 和 <code>n</code> 。其中 <code>nums1</code> 实际长度为 <code>m+n</code> ， <code>nums2</code> 实际长度为 <code>n</code> ，请合并 <code>nums2</code> 到 <code>nums1</code> 中去，且合并后的数组 <code>nums1</code> 仍保持非递减顺序。注意： <code>nums1</code> 前 <code>m</code> 个元素表示其有效元素，后 <code>n</code> 个元素为 <code>0</code> 。</p> <p><a rel="external" href="https://leetcode.cn/problems/merge-sorted-array/">88. 合并两个有序数组</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-pai-xu-fa">1 排序法</h3> <h4 id="fen-xi">分析</h4> <p>直接合并两个数组，然后排序。</p> <h4 id="dai-ma">代码</h4> <ul> <li> <p>将数组 <code>nums2</code> 拼接至 <code>nums1</code> 后半部分</p> </li> <li> <p>非递减排序 <code>nums1</code></p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> merge</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums1</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> m</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums2</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> n</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历nums2</span></span> <span class="giallo-l"><span class="z-source"> nums1</span><span class="z-punctuation">[</span><span class="z-source">m </span><span class="z-keyword z-operator">+</span><span class="z-source"> i</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-source"> nums2</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">];</span><span class="z-punctuation z-definition z-comment z-comment"> // 将nums2中元素挪至nums1后半部分</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> sort</span><span class="z-punctuation">(</span><span class="z-source">nums1</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">begin</span><span class="z-punctuation">(),</span><span class="z-source"> nums1</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">end</span><span class="z-punctuation">());</span><span class="z-punctuation z-definition z-comment z-comment"> // 非递减排序nums1</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <p>时间复杂度为 <code>O((m+n)log(m+n))</code> ，空间复杂度为 <code>O(log(m+n))</code> ，即快速排序长度为 <code>m+n</code> 数组的复杂度。</p> <h3 id="2-shuang-zhi-zhen">2 双指针</h3> <h4 id="fen-xi-1">分析</h4> <p>因为数组 <code>nums1</code> 和 <code>nums2</code> 本是有序数组，因此使用双指针很容易获得二者结合的有序序列：从前往后遍历两数组，取二者元素的较小者，顺序放入结果数组；或从后往前遍历两数组，取二者元素的较大者，逆序放入结果数组。</p> <p>我们本需要额外分配 <code>m+n</code> 的空间来存放结果数组，但 <code>nums1</code> 已在数组末尾分配好额外大小为 <code>n</code> 的空间。此时可发现，使用从后往前的遍历方法，无需考虑覆盖数组 <code>nums1</code> 元素的问题，也无需分配额外空间。</p> <h4 id="dai-ma-1">代码</h4> <ul> <li> <p>初始化两指针 <code>left</code> 和 <code>right</code> 分别指向 <code>nums1</code> 和 <code>nums2</code> 的有效末尾元素，再初始化一指针 <code>cur</code> 指向 <code>nums1</code> 实际末尾元素</p> </li> <li> <p>遍历 <code>nums1</code> 和 <code>nums2</code> 直到完成其中一个</p> </li> <li> <p>拷贝 <code>left</code> 和 <code>right</code> 指向元素的较大者至 <code>cur</code> ，更新指针</p> </li> <li> <p>遍历完后，拷贝 <code>nums2</code> 剩余（如果存在）至 <code>nums1</code></p> </li> <li> <p>注：无需考虑 <code>nums1</code> 存在剩余的情况</p> </li> </ul> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> void</span><span class="z-entity z-name z-function"> merge</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums1</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> m</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> vector</span><span class="z-punctuation">&lt;</span><span class="z-storage z-type">int</span><span class="z-punctuation">&gt;</span><span class="z-storage z-modifier z-reference z-cpp">&amp;</span><span class="z-variable z-parameter"> nums2</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-variable z-parameter"> n</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> left </span><span class="z-keyword z-operator">=</span><span class="z-source"> m </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">,</span><span class="z-source"> right </span><span class="z-keyword z-operator">=</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 指向nums1、nums2末尾有效元素的指针left、right</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> cur </span><span class="z-keyword z-operator">=</span><span class="z-source"> m </span><span class="z-keyword z-operator">+</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 指向nums1末尾的指针cur</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">left </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-keyword z-operator"> &amp;&amp;</span><span class="z-source"> right </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历nums1和nums2直到其中一个完成</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">nums1</span><span class="z-punctuation">[</span><span class="z-source">left</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> &gt;=</span><span class="z-source"> nums2</span><span class="z-punctuation">[</span><span class="z-source">right</span><span class="z-punctuation">]) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 取其中较大者存入位置cur</span></span> <span class="giallo-l"><span class="z-source"> nums1</span><span class="z-punctuation">[</span><span class="z-source">cur</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-source"> nums1</span><span class="z-punctuation">[</span><span class="z-source">left</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> --</span><span class="z-source">left</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> nums1</span><span class="z-punctuation">[</span><span class="z-source">cur</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-source"> nums2</span><span class="z-punctuation">[</span><span class="z-source">right</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> --</span><span class="z-source">right</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> --</span><span class="z-source">cur</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 更新cur</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">right </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 完成nums2剩余遍历（如果需要）</span></span> <span class="giallo-l"><span class="z-source"> nums1</span><span class="z-punctuation">[</span><span class="z-source">cur</span><span class="z-keyword z-operator">--</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-source"> nums2</span><span class="z-punctuation">[</span><span class="z-source">right</span><span class="z-keyword z-operator">--</span><span class="z-punctuation">];</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 注：无需考虑num1的剩余遍历</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du-1">复杂度</h4> <ul> <li> <p>最坏情况下，指针移动 <code>m+n</code> 次（ <code>nums1</code> 的最小元素大于 <code>nums2</code> 的最大元素），时间复杂度为 <code>O(m+n)</code></p> </li> <li> <p>数组原地操作，空间复杂度为 <code>O(1)</code></p> </li> </ul> <hr /> <h3 id="san-zong-jie">三 总结</h3> <ul> <li>当需要原地操作数组时，考虑双指针法以有效提升时间和空间复杂度。</li> </ul> <hr /> <p>​</p> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/07-roman-to-integer/ <h2 id="yi-wen-ti-miao-shu">一 问题描述</h2> <p>罗马数字包含七种字符： <code>I</code> ， <code>V</code> ， <code>X</code> ， <code>L</code> ， <code>C</code> ， <code>D</code> ， <code>M</code> 。</p> <table><thead><tr><th style="text-align: center">字符</th><th style="text-align: center">数值</th></tr></thead><tbody> <tr><td style="text-align: center"><code>I</code></td><td style="text-align: center">1</td></tr> <tr><td style="text-align: center"><code>V</code></td><td style="text-align: center">5</td></tr> <tr><td style="text-align: center"><code>X</code></td><td style="text-align: center">10</td></tr> <tr><td style="text-align: center"><code>L</code></td><td style="text-align: center">50</td></tr> <tr><td style="text-align: center"><code>C</code></td><td style="text-align: center">100</td></tr> <tr><td style="text-align: center"><code>D</code></td><td style="text-align: center">500</td></tr> <tr><td style="text-align: center"><code>M</code></td><td style="text-align: center">1000</td></tr> </tbody></table> <p>例如：罗马数字 <code>2</code> 写做 <code>II</code> ， <code>12</code> 写做 <code>XII</code> ， <code>27</code> 写做 <code>XXVII</code> 。</p> <p>通常情况下罗马数字中小的数字在大的数字右边，但也有特例。如 <code>4</code> 不写做 <code>IIII</code> ，而是 <code>IV</code> ， <code>9</code> 写做 <code>IX</code> 。这个特殊规则如下：</p> <ul> <li> <p><code>I</code> 可以放在 <code>V</code> 和 <code>X</code> 的左边，来表示 <code>4</code> 和 <code>9</code></p> </li> <li> <p><code>X</code> 可以放在 <code>L</code> 和 <code>C</code> 的左边，来表示 <code>40</code> 和 <code>90</code></p> </li> <li> <p><code>C</code> 可以放在 <code>D</code> 和 <code>M</code> 的左边，来表示 <code>400</code> 和 <code>900</code></p> </li> </ul> <p>给定一个表示罗马数字的字符串，将其转换为整数。</p> <p><a rel="external" href="https://leetcode.cn/problems/roman-to-integer/">13. 罗马数字转整数</a></p> <hr /> <h2 id="er-jie-jue-fang-fa">二 解决方法</h2> <h3 id="1-mo-ni">1 模拟</h3> <h4 id="fen-xi">分析</h4> <p>不考虑特殊情况，罗马数字中的七种字符分别代表7个不同数值。也就是说：只要将字符串的每一个字符转换成对应的数值，然后将其累加起来，就可以得到其对应整数。</p> <p>考虑特殊情况，当位于左边的罗马数字小于其右边的时，左边罗马数字取负。</p> <p>使用哈希表存储罗马字符与对应数值的映射关系，便于使用。</p> <h4 id="dai-ma">代码</h4> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">class</span><span class="z-entity z-name z-type"> Solution</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type">public</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-entity z-name z-function"> romanToInt</span><span class="z-punctuation">(</span><span class="z-entity z-name z-type">string</span><span class="z-variable z-parameter"> s</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> unordered_map</span><span class="z-keyword z-operator">&lt;</span><span class="z-storage z-type">char</span><span class="z-punctuation">,</span><span class="z-storage z-type"> int</span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> _map </span><span class="z-keyword z-operator">=</span><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-comment z-comment"> // 罗马字符-数值映射表</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;I&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;V&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 5</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;X&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 10</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;L&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 50</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;C&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;D&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 500</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span><span class="z-punctuation z-definition z-string z-string">&#39;M&#39;</span><span class="z-punctuation">,</span><span class="z-constant z-numeric"> 1000</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-punctuation"> };</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> s</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">size</span><span class="z-punctuation">();</span><span class="z-punctuation z-definition z-comment z-comment"> // 字符串长度</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 初始化总和为0（返回值）</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 遍历罗马数字字符串</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> value </span><span class="z-keyword z-operator">=</span><span class="z-source"> _map</span><span class="z-punctuation">[</span><span class="z-source">s</span><span class="z-punctuation">[</span><span class="z-source">i</span><span class="z-punctuation">]];</span><span class="z-punctuation z-definition z-comment z-comment"> // 根据映射表获取当前字符数值</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n </span><span class="z-keyword z-operator">-</span><span class="z-constant z-numeric"> 1</span><span class="z-keyword z-operator"> &amp;&amp;</span><span class="z-source"> value </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> _map</span><span class="z-punctuation">[</span><span class="z-source">s</span><span class="z-punctuation">[</span><span class="z-source">i </span><span class="z-keyword z-operator">+</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">]]) {</span><span class="z-punctuation z-definition z-comment z-comment"> // 考虑特殊情况</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">-=</span><span class="z-source"> value</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 当前数值小于右侧数值，取负值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-keyword"> else</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> value</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 否则取正值</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-source"> sum</span><span class="z-punctuation">;</span><span class="z-punctuation z-definition z-comment z-comment"> // 返回总和</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span></code></pre><h4 id="fu-za-du">复杂度</h4> <ul> <li> <p>只遍历长度为 <code>n</code> 的字符串一次，因此时间复杂度为 <code>O(n)</code> 。</p> </li> <li> <p>只使用常量个变量，因此空间复杂度为 <code>O(1)</code> 。</p> </li> </ul> <hr /> <h2 id="san-zong-jie">三 总结</h2> <ul> <li>有些问题只能根据题意模拟它的解决思路，并没有其他巧妙的方法。</li> </ul> <hr /> 2024-11-09T00:00:00+00:00 2024-11-09T00:00:00+00:00 shaozk https://shaozk.xyz/csdn/08-cpp-primer-chapter-1-exercises/ <h2 id="xi-ti">习题</h2> <h3 id="lian-xi-1-1">练习 1.1</h3> <p>查阅你使用的编译器的文档，确定它所使用的文件命名约定。编译并运行第2页的 <code>main</code> 程序。</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> man g++</span></span> <span class="giallo-l"><span class="z-support z-function z-builtin">...</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 头文件</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.hh</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.H</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.hp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.hxx</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.hpp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.HPP</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.h++</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.tcc</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> C++</span><span class="z-string"> header file to be turned into a precompiled header or Ada spec.</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 源文件</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.cc</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.cp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.cxx</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.cpp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.CPP</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.c++</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> file.C</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> C++</span><span class="z-string"> source code that must be preprocessed. Note that in .cxx, the last two letters must both be literally x. Likewise, .C refers to a</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> literal</span><span class="z-string"> capital C.</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-support z-function z-builtin">...</span></span></code></pre><pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_1.cpp</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_1.out demo1_1.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_1.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> echo</span><span class="z-punctuation z-definition z-variable z-source"> $?</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0</span></span></code></pre><h3 id="lian-xi-1-2">练习 1.2</h3> <p>改写程序，让它返回-1。返回值-1通常被当做程序错误的标识。重新编译并运行你的程序，观察你的系统如何处理 <code>main</code> 返回的错误标识符。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_2.cpp</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_2.out demo1_2.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_2.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> echo</span><span class="z-punctuation z-definition z-variable z-source"> $?</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">255</span></span></code></pre><h3 id="lian-xi-1-3">练习 1.3</h3> <p>编写程序，在标准输出上打印 Hello, World。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_3.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Hello, Wolrd&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_3.out demo1_3.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_3.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Hello,</span><span class="z-string"> Wolrd</span></span></code></pre><h3 id="lian-xi-1-4">练习 1.4</h3> <p>我们的程序使用加法运算符 <code>+</code> 来将两个数相加。编写程序使用乘法运算符来打印两个数的积。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_4.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; * &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; = &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">*</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_4.out demo1_4.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_4.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-constant z-numeric"> 4</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-variable"> *</span><span class="z-constant z-numeric"> 4</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 12</span></span></code></pre><h3 id="lian-xi-1-5">练习 1.5</h3> <p>我们将所有的输出操作放在一个很长的语句中。重写程序，将每个运算对象的打印操作放在一条独立的语句中。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_5.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> v1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> v1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; * &quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; = &quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">*</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_5.out demo1_5.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_5.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-variable"> *</span><span class="z-constant z-numeric"> 5</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 15</span></span></code></pre><h3 id="lian-xi-1-6">练习 1.6</h3> <p>解释下面程序片段是否合法。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;The sum of &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; and &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; is &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">+</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span></code></pre> <p>如果程序是合法的，它输出什么？如果程序不合法，原因何在？应该如何修正？</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_6.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;The sum of &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; and &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; is &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> v1 </span><span class="z-keyword z-operator">+</span><span class="z-source"> v2 </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 不合法，将会报语法错误。因为第一行由&#39;;&#39;结束，说明是一条完整的语句，而第二行输出运算符&#39;&lt;&lt;&#39;左边必须是一个ostream流类型对象，所以会报语法错误。</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 错误信息：</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_6.out demo1_6.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_6.cpp:</span><span class="z-string"> In function ‘int main</span><span class="z-punctuation">()</span><span class="z-string">’:</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_6.cpp:9:9:</span><span class="z-string"> error: expected primary-expression before ‘</span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string">’</span><span class="z-entity z-name z-function"> token</span></span> <span class="giallo-l"><span class="z-string"> 9 | &lt;&lt; &quot; and &quot; &lt;&lt; v2;</span></span> <span class="giallo-l"><span class="z-string"> | ^~</span></span> <span class="giallo-l"><span class="z-string">demo1_6.cpp:10:9: error: expected primary-expression before ‘&lt;&lt;’ token</span></span> <span class="giallo-l"><span class="z-string"> 10 | &lt;&lt; &quot; is &quot; &lt;&lt; v1 + v2 &lt;&lt; std::endl;</span></span> <span class="giallo-l"><span class="z-string"> | ^~</span></span> <span class="giallo-l"><span class="z-string"> </span></span> <span class="giallo-l"><span class="z-string"># 将每行代码末尾分号&#39;;&#39;移除即可修正，具体代码如下：</span></span> <span class="giallo-l"><span class="z-string">std::cout &lt;&lt; &quot;The sum of &quot; &lt;&lt; v1</span></span> <span class="giallo-l"><span class="z-string"> &lt;&lt; &quot; and &quot; &lt;&lt; v2</span></span> <span class="giallo-l"><span class="z-string"> &lt;&lt; &quot; is &quot; &lt;&lt; v1 + v2 &lt;&lt; std::endl;</span></span></code></pre><h3 id="lian-xi-1-7">练习 1.7</h3> <p>编译一个包含不正确的嵌套注释的程序，观察编译器返回的错误信息。</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_7.out demo1_7.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_7.cpp:</span><span class="z-string"> In function ‘int main</span><span class="z-punctuation">()</span><span class="z-string">’:</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_7.cpp:5:11:</span><span class="z-string"> error: expected primary-expression before ‘/’ token</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> 5</span><span class="z-keyword z-operator"> |</span><span class="z-entity z-name z-function"> /*</span><span class="z-variable"> *</span><span class="z-string">/</span><span class="z-variable">*</span><span class="z-string">/</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> |</span><span class="z-entity z-name z-function"> ^</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_7.cpp:6:5:</span><span class="z-string"> error: expected primary-expression before ‘return’</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> 6</span><span class="z-keyword z-operator"> |</span><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> |</span><span class="z-entity z-name z-function"> ^~~~~~</span></span></code></pre><h3 id="lian-xi-1-8">练习 1.8</h3> <p>指出下列哪些输出语句是合法的（如果有的话）：</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;/*&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;*/&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-comment z-comment"> /* &quot;*/</span><span class="z-punctuation z-definition z-string z-string">&quot; */;</span></span> <span class="giallo-l"><span class="z-string z-punctuation z-definition z-string">std::cout &lt;&lt; /* &quot;</span><span class="z-source">*/</span><span class="z-punctuation z-definition z-string z-string">&quot; /* &quot;</span><span class="z-punctuation z-definition z-comment z-comment">/*&quot; */</span><span class="z-punctuation">;</span></span></code></pre> <p>预测编译这些语句会产生什么样的结果，实际编译这些语句来验证你的答案（编写一个小程序，每次将上述一条语句作为其主体），改正每个编译错误。</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-string"> 正确</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-string"> 正确</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-string"> 错误 双引号缺少结束符</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">4</span><span class="z-string"> 正确</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">//</span><span class="z-string"> demo1_8_1.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">#include &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function">int</span><span class="z-string"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> std::cout</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot;/*&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-string"> return 0;</span></span> <span class="giallo-l"><span class="z-string">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_8_1.out demo1_8_1.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_8_1.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">/*$</span><span class="z-source"> </span></span></code></pre><pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_8_2.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;*/&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">/*g++</span><span class="z-string"> -o demo1_8_2.out demo1_8_2.cpput</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_8_2.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword z-operator">*</span><span class="z-source">/$ </span></span></code></pre><pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_8_3.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-comment z-comment"> /* &quot;*/</span><span class="z-punctuation z-definition z-string z-string">&quot; */;</span></span> <span class="giallo-l"><span class="z-string"> return 0;</span></span> <span class="giallo-l"><span class="z-string">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-keyword z-operator">*</span><span class="z-source">/g++ -o demo1_8_3.out demo1_8_3.cpput </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_8_3.cpp:6:24:</span><span class="z-string z-punctuation z-definition z-string"> warning: missing terminating &quot; character</span></span> <span class="giallo-l"><span class="z-string z-punctuation z-definition z-string"> 6 | std::cout &lt;&lt; /* &quot;</span><span class="z-variable">*</span><span class="z-string z-punctuation z-definition z-string">/&quot; */;</span></span> <span class="giallo-l"><span class="z-string"> | ^</span></span> <span class="giallo-l"><span class="z-string z-punctuation z-definition z-string">demo1_8_3.cpp:6:24: error: missing terminating &quot; character</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> 6</span><span class="z-keyword z-operator"> |</span><span class="z-entity z-name z-function"> std::cout</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string"> /*</span><span class="z-entity z-name z-function"> &quot;*/&quot;</span><span class="z-variable"> *</span><span class="z-string">/</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-string"> | ^~~~~</span></span> <span class="giallo-l"><span class="z-string">demo1_8_3.cpp: In function ‘int main()’:</span></span> <span class="giallo-l"><span class="z-string">demo1_8_3.cpp:7:5: error: expected primary-expression before ‘return’</span></span> <span class="giallo-l"><span class="z-string"> 7 | return 0;</span></span> <span class="giallo-l"><span class="z-string"> | ^~~~~~</span></span></code></pre><pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-source">$ g</span><span class="z-keyword z-operator">++ -</span><span class="z-source">o demo1_8_4</span><span class="z-punctuation">.</span><span class="z-source">out demo1_8_4</span><span class="z-punctuation">.</span><span class="z-source">cpp </span></span> <span class="giallo-l"><span class="z-source">$ .</span><span class="z-keyword z-operator">/</span><span class="z-source">demo1_8_4</span><span class="z-punctuation">.</span><span class="z-source">out </span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> /* $ </span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_8_4.out demo1_8_4.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_8_4.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> /*</span><span class="z-source"> $ </span></span></code></pre><h3 id="lian-xi-1-9">练习 1.9</h3> <p>编写程序，使用 <code>while</code> 循环将50到100的整数相加。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_9.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> a </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 50</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source"> a </span><span class="z-keyword z-operator">&lt;=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> a</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> a</span><span class="z-keyword z-operator">++</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;sum = &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> sum </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> /g++ -o demo1_9.out demo1_9.cpp.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_9.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sum</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 3825</span></span></code></pre><h3 id="lian-xi-1-10">练习 1.10</h3> <p>除了 <code>++</code> 运算符将运算对象的值增加1之外，还有一个递减运算符（ <code>--</code> ）实现将值减少1。编写程序，使用递减运算符在循环中按递减顺序打印出10到0之间的整数。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_10.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> a </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 10</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source"> a </span><span class="z-keyword z-operator">&gt;=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> a </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> a</span><span class="z-keyword z-operator">--</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_10.out demo1_10.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_10.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">10</span><span class="z-constant z-numeric"> 9 8 7 6 5 4 3 2 1 0</span><span class="z-source"> </span></span></code></pre><h3 id="lian-xi-1-11">练习 1.11</h3> <p>编写程序，提示用户输入两个整数，打印这两个整数所有指定的范围内的所有整数。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_11.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> a </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> b </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> cur </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Input two number:</span><span class="z-constant z-character z-escape">\n</span><span class="z-punctuation z-definition z-string">&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> a </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> b</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">a </span><span class="z-keyword z-operator">&lt;=</span><span class="z-source"> b</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cur </span><span class="z-keyword z-operator">=</span><span class="z-source"> a</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">cur </span><span class="z-keyword z-operator">&lt;=</span><span class="z-source"> b</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> cur </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> cur</span><span class="z-keyword z-operator">++</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> else</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cur </span><span class="z-keyword z-operator">=</span><span class="z-source"> a</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">cur </span><span class="z-keyword z-operator">&gt;=</span><span class="z-source"> b</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> cur </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-source"> cur</span><span class="z-keyword z-operator">--</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_11.out demo1_11.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_11.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Input</span><span class="z-string"> two number:</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-constant z-numeric"> 3 4 5</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_11.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Input</span><span class="z-string"> two number:</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">5</span><span class="z-constant z-numeric"> 2</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">5</span><span class="z-constant z-numeric"> 4 3 2</span><span class="z-source"> </span></span></code></pre><h3 id="lian-xi-1-12">练习 1.12</h3> <p>下面的 <code>for</code> 循环完成了什么功能？sum的终值是多少？</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword">for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> i</span><span class="z-punctuation">;</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 计算从0到100之间整数的总和</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 5050</span></span></code></pre><pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_12.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> i</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;sum = &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> sum </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ -o demo1_12.out demo1_12.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./demo1_12.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sum</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 5050</span></span></code></pre><h3 id="lian-xi-1-13">练习 1.13</h3> <p>使用 <code>for</code> 循环重做1.4.1节中的所有练习（第11页）。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_13_1.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> num </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 50</span><span class="z-punctuation">;</span><span class="z-source"> num </span><span class="z-keyword z-operator">&lt;=</span><span class="z-constant z-numeric"> 100</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">num</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> num</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;sum = &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> sum </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_13_2.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 10</span><span class="z-punctuation">;</span><span class="z-source"> n </span><span class="z-keyword z-operator">&gt;</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> --</span><span class="z-source">n</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;n = &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> n </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_13_3.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-storage z-type">using namespace</span><span class="z-entity z-name z-namespace"> std</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> m</span><span class="z-punctuation">,</span><span class="z-source"> n</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Please input 2 number:&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> m </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">m </span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> n</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> tmp </span><span class="z-keyword z-operator">=</span><span class="z-source"> m</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> m </span><span class="z-keyword z-operator">=</span><span class="z-source"> n</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> n </span><span class="z-keyword z-operator">=</span><span class="z-source"> tmp</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-source"> m</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># demo1_13_1.cpp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_13_1.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sum</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 3825</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># demo1_13_2.cpp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_13_2.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 10</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 9</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 8</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 7</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 6</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 5</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 4</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 3</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 2</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">n</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 1</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># demo1_13_3.cpp</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_13_3.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Please</span><span class="z-string"> input</span><span class="z-constant z-numeric"> 2</span><span class="z-string"> number:10</span><span class="z-constant z-numeric"> 1</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-constant z-numeric"> 2 3 4 5 6 7 8 9</span><span class="z-source"> </span></span> <span class="giallo-l"></span></code></pre><h3 id="lian-xi-1-14">练习 1.14</h3> <p>对比 <code>for</code> 循环和 <code>while</code> 循环，两种形式的优缺点各是什么？</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 对于for循环，有三个控制条件：初始值、结束值和步进值，其形式更为集中、简洁，且适用于循环次数已知的情况。</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 对于while循环，使用特定条件控制循环是否执行，适用于循环次数未知的情况。</span></span></code></pre><h3 id="lian-xi-1-15">练习 1.15</h3> <p>编写程序，包含第14页“再探编译”中讨论的常见错误。熟悉编译器生成的错误信息。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_15.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 错误：endl后使用了冒号而非分号</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Read each file.&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">:</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 错误：字符串字面值常量的两侧漏掉了引号</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> Update master. </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 错误：漏掉了第二个输出运算符</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Write new master.&quot;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"> // 错误：return语句漏掉了分号</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 其中只有最后一个错误精准找到了 </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_15.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_15.cpp:</span><span class="z-string"> In function ‘int main</span><span class="z-punctuation">()</span><span class="z-string">’:</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">demo1_15.cpp:6:48:</span><span class="z-string"> error: found ‘:’ in nested-name-specifier, expected ‘::’</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> 6</span><span class="z-keyword z-operator"> |</span><span class="z-entity z-name z-function"> std::cout</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot;Read each file.&quot;</span><span class="z-source"> &lt;&lt;</span><span class="z-entity z-name z-function"> std::endl:</span></span> <span class="giallo-l"><span class="z-string"> | ^</span></span> <span class="giallo-l"><span class="z-string"> | ::</span></span> <span class="giallo-l"><span class="z-string">demo1_15.cpp:6:44: error: ‘std::endl’ is not a class, namespace, or enumeration</span></span> <span class="giallo-l"><span class="z-string"> 6 | std::cout &lt;&lt; &quot;Read each file.&quot; &lt;&lt; std::endl:</span></span> <span class="giallo-l"><span class="z-string"> | ^~~~</span></span> <span class="giallo-l"><span class="z-string">demo1_15.cpp:7:18: error: ‘Update’ was not declared in this scope</span></span> <span class="giallo-l"><span class="z-string"> 7 | std::cout &lt;&lt; Update master. &lt;&lt; std::endl;</span></span> <span class="giallo-l"><span class="z-string"> | ^~~~~~</span></span> <span class="giallo-l"><span class="z-string">demo1_15.cpp:8:37: error: expected ‘;’ before ‘std’</span></span> <span class="giallo-l"><span class="z-string"> 8 | std::cout &lt;&lt; &quot;Write new master.&quot; std::endl;</span></span> <span class="giallo-l"><span class="z-string"> | ^~~~</span></span> <span class="giallo-l"><span class="z-string"> | ;</span></span> <span class="giallo-l"><span class="z-string">demo1_15.cpp:9:13: error: expected ‘;’ before ‘}’ token</span></span> <span class="giallo-l"><span class="z-string"> 9 | return 0</span></span> <span class="giallo-l"><span class="z-string"> | ^</span></span> <span class="giallo-l"><span class="z-string"> | ;</span></span> <span class="giallo-l"><span class="z-string"> 10 | }</span></span> <span class="giallo-l"><span class="z-string"> | ~ </span></span> <span class="giallo-l"></span></code></pre><h3 id="lian-xi-1-16">练习 1.16</h3> <p>编写程序，从 <code>cin</code> 读取一组数，输出其和。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_16.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> value </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> value</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> value</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;sum = &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> sum </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_16.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-constant z-numeric"> 4</span><span class="z-string"> 5^E</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">sum</span><span class="z-string"> =</span><span class="z-constant z-numeric"> 12</span></span></code></pre><h3 id="lian-xi-1-17">练习 1.17</h3> <p>如果输入的所有值是相等的，本节的程序会输出什么？如果没有重复值，输出又会是什么？</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 当输入的所有值是相等时，程序会计算该值出现的次数。</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 没有重复值时，每个值计数一次</span></span></code></pre><h3 id="lian-xi-1-18">练习 1.18</h3> <p>编译并运行本节的程序，给它输入全都相等的值。再次运行程序，输入没有重复的值。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_17.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> currVal </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">,</span><span class="z-source"> val </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> currVal</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> val</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">val </span><span class="z-keyword z-operator">==</span><span class="z-source"> currVal</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">cnt</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> else</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> currVal </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; occurs &quot;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; times&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> currVal </span><span class="z-keyword z-operator">=</span><span class="z-source"> val</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> currVal </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; occurs &quot;</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot; times&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_18.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-constant z-numeric"> 1 1 1 1 1 1</span><span class="z-string"> 1^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 8</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-constant z-numeric"> 2 3 4 5 6 7 8</span><span class="z-string"> 9^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">2</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">3</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">4</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">5</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">6</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">7</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">8</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">9</span><span class="z-string"> occurs</span><span class="z-constant z-numeric"> 1</span><span class="z-string"> times</span></span></code></pre><h3 id="lian-xi-1-19">练习 1.19</h3> <p>修改你为1.4.1节练习1.10（第11页）所编写的程序（打印一个范围内的数），使其能处理用户输入的第一个数比第二个数小的情况。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_19.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-storage z-type">using namespace</span><span class="z-entity z-name z-namespace"> std</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> m</span><span class="z-punctuation">,</span><span class="z-source"> n</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;Please input 2 number:&quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> m </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">m </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-source"> m</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> ++</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> else</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-punctuation"> (</span><span class="z-storage z-type">int</span><span class="z-source"> i </span><span class="z-keyword z-operator">=</span><span class="z-source"> m</span><span class="z-punctuation">;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&gt;</span><span class="z-source"> n</span><span class="z-punctuation">;</span><span class="z-keyword z-operator"> --</span><span class="z-source">i</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> i </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_19.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Please</span><span class="z-string"> input</span><span class="z-constant z-numeric"> 2</span><span class="z-string"> number:1</span><span class="z-constant z-numeric"> 10</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">1</span><span class="z-constant z-numeric"> 2 3 4 5 6 7 8 9</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">Please</span><span class="z-string"> input</span><span class="z-constant z-numeric"> 2</span><span class="z-string"> number:10</span><span class="z-constant z-numeric"> 1</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">10</span><span class="z-constant z-numeric"> 9 8 7 6 5 4 3 2</span><span class="z-source"> </span></span></code></pre><h3 id="lian-xi-1-20">练习 1.20</h3> <p>在网站http://www.informit.com/title/03217714113 上，第1章的代码目录包含了头文件 <code>Sales_item.h</code> 。将它拷贝到你自己的工作目录。用它编写一个程序，读取一组书籍销售记录，将每条记录打印到标准输出上。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_20.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &quot;include/Sales_item.h&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-storage z-type">using namespace</span><span class="z-entity z-name z-namespace"> std</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> Sales_item item</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> item</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> item </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_20.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 3 20.00</span><span class="z-string"> 0-201-78346-X</span><span class="z-constant z-numeric"> 4 40.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 3 60 20</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78346-X</span><span class="z-constant z-numeric"> 4 160 40</span></span></code></pre><h3 id="lian-xi-1-21">练习 1.21</h3> <p>编写程序，读取两个ISBN相同的 <code>Sales_Item</code> 对象，输出它们的和。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_21.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &quot;include/Sales_item.h&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-storage z-type">using namespace</span><span class="z-entity z-name z-namespace"> std</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> Sales_item item1</span><span class="z-punctuation">,</span><span class="z-source"> item2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> item1 </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> item2</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">item1</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> ==</span><span class="z-source"> item2</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">())</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> item1 </span><span class="z-keyword z-operator">+</span><span class="z-source"> item2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_21.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 3 20.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 5 20.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 8 160 20</span><span class="z-source">$ </span></span></code></pre><h3 id="lian-xi-1-22">练习 1.22</h3> <p>编写程序，读取多个具有相同ISBN的销售记录，输出所有记录的和。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_22.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &quot;include/Sales_item.h&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-storage z-type">using namespace</span><span class="z-entity z-name z-namespace"> std</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> Sales_item item</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> Sales_item sum</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> item</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">=</span><span class="z-source"> item</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> item</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">item</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> ==</span><span class="z-source"> sum</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">())</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> sum </span><span class="z-keyword z-operator">+=</span><span class="z-source"> item</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> sum </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 3 20.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 4 20.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 5</span><span class="z-string"> 20.00^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 12 240 20</span></span></code></pre><h3 id="lian-xi-1-23">练习 1.23</h3> <p>编写程序，读取多条销售记录，并统计一个ISBN（每本书）有几条销售记录。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_23.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &quot;include/Sales_item.h&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-storage z-type">using namespace</span><span class="z-entity z-name z-namespace"> std</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> Sales_item start</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> start</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type"> int</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> Sales_item item</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> item</span><span class="z-punctuation">)</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">item</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> ==</span><span class="z-source"> start</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">())</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> ++</span><span class="z-source">cnt</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> else</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> start</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> cnt </span><span class="z-keyword z-operator">=</span><span class="z-constant z-numeric"> 1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> start </span><span class="z-keyword z-operator">=</span><span class="z-source"> item</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-source"> cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> start</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-punctuation z-definition z-string"> &quot; &quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-source"> cnt </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_23.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 4 20.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 6 30.00</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78346-X</span><span class="z-constant z-numeric"> 7</span><span class="z-string"> 30.00^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 2</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">^E</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78346-X</span><span class="z-constant z-numeric"> 1</span></span></code></pre><h3 id="lian-xi-1-24">练习 1.24</h3> <p>输入表示多个ISBN的多条销售记录来测试上一个程序，每个ISBN的记录应该聚在一起。</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment"># 见习题1.23</span></span></code></pre><h3 id="lian-xi-1-25">练习 1.25</h3> <p>借助网站上的 <code>Sales_Item.h</code> 头文件，编译并运行本节给出的书店程序。</p> <pre class="giallo z-code"><code data-lang="cpp"><span class="giallo-l"><span class="z-punctuation z-definition z-comment z-comment">// demo1_25.cpp</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &lt;iostream&gt;</span></span> <span class="giallo-l"><span class="z-punctuation z-definition z-directive z-keyword z-control z-directive">#include</span><span class="z-punctuation z-definition z-string z-string"> &quot;include/Sales_item.h&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">int</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">()</span></span> <span class="giallo-l"><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-source"> Sales_item total</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> total</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> Sales_item trans</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> while</span><span class="z-punctuation"> (</span><span class="z-entity z-name z-scope-resolution z-cpp">std</span><span class="z-punctuation">::</span><span class="z-source">cin </span><span class="z-keyword z-operator">&gt;&gt;</span><span class="z-source"> trans</span><span class="z-punctuation">)</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-keyword"> if</span><span class="z-punctuation"> (</span><span class="z-source">total</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">()</span><span class="z-keyword z-operator"> ==</span><span class="z-source"> trans</span><span class="z-punctuation">.</span><span class="z-entity z-name z-function">isbn</span><span class="z-punctuation">())</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-source"> total </span><span class="z-keyword z-operator">+=</span><span class="z-source"> trans</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> else</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> total </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-source"> total </span><span class="z-keyword z-operator">=</span><span class="z-source"> trans</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cout </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-source"> total </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-keyword"> else</span></span> <span class="giallo-l"><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">cerr </span><span class="z-keyword z-operator">&lt;&lt;</span><span class="z-punctuation z-definition z-string z-string"> &quot;No data?&quot;</span><span class="z-keyword z-operator"> &lt;&lt;</span><span class="z-entity z-name z-scope-resolution z-cpp"> std</span><span class="z-punctuation">::</span><span class="z-source">endl</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-keyword z-operator"> -</span><span class="z-constant z-numeric">1</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-keyword"> return</span><span class="z-constant z-numeric"> 0</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> g++ demo1_25.cpp</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">$</span><span class="z-string"> ./a.out</span><span class="z-source"> </span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 3 20.0</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 2 25.0</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78346-X</span><span class="z-constant z-numeric"> 4 40.0</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78345-X</span><span class="z-constant z-numeric"> 5 110 22</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78347-X</span><span class="z-constant z-numeric"> 7 70.0</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78346-X</span><span class="z-constant z-numeric"> 4 160 40</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">^E</span></span> <span class="giallo-l"><span class="z-entity z-name z-function">0-201-78347-X</span><span class="z-constant z-numeric"> 7 490 70</span></span></code></pre><h2 id="zong-jie">总结</h2> <p>第一章总体来说十分简单，主要介绍有：</p> <ul> <li> <p>C++程序的编译与运行</p> </li> <li> <p>输入与输出（ <code>std::cin</code> 和 <code>std::cout</code> ）</p> </li> <li> <p>注释（ <code>//</code> 和 <code>/* */</code> ）</p> </li> <li> <p>控制语句，包括 <code>while</code> 循环、 <code>for</code> 循环和 <code>if</code> 语句</p> </li> <li> <p>类简单使用，包括对象声明、类的成员函数调用以及类的 <code>+ - * / =</code> 操作（前提是需要在类定义时重载这些运算符）</p> </li> </ul>