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search.xml
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<?xml version="1.0" encoding="utf-8"?>
<search>
<entry>
<title>C++面向对象的三大特性</title>
<url>/posts/ac27/</url>
<content><![CDATA[]]></content>
<categories>
<category>C++</category>
</categories>
<tags>
<tag>C++</tag>
<tag>面向对象</tag>
</tags>
</entry>
<entry>
<title>Github下载加速</title>
<url>/posts/79ca/</url>
<content><![CDATA[<p><strong>准备条件</strong></p>
<ul>
<li>码云(Gitee账号)</li>
</ul>
<p>注册地址：<a href="https://gitee.com/" target="_blank" rel="noopener">https://gitee.com/</a></p>
<ul>
<li>Git</li>
</ul>
<p>镜像下载地址：<a href="https://npm.taobao.org/mirrors/git-for-windows" target="_blank" rel="noopener">https://npm.taobao.org/mirrors/git-for-windows</a></p>
<h2 id="1-码云-Gitee-导入"><a href="#1-码云-Gitee-导入" class="headerlink" title="1.码云(Gitee)导入"></a>1.码云(Gitee)导入</h2><p>1.以<code>Github</code>上Stars较多的一个优秀的Java学习路线项目为例</p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/6e61b1ed8495188950dfd0b73705b957.png" alt="image-20200630113350201"></p>
<blockquote>
<p>1.复制项目的网址</p>
</blockquote>
<p><a href="https://github.com/Snailclimb/JavaGuide" target="_blank" rel="noopener">https://github.com/Snailclimb/JavaGuide</a></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/b5928fa75fe216915bfa5f0611796b28.png" alt="image-20200630113456261"></p>
<blockquote>
<p>2.导入项目到Gitee</p>
</blockquote>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/d2e4a08b94327d6b0ce9569607ee63f2.png" alt="image-20200630113727080"></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/1202564fd464d7efa445f44a5679d0a8.png" alt="image-20200630114432345"></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/4d52e8150d9f81182e386a8882d4d70f.png" alt="image-20200630114647419"></p>
<p><strong>导入后等待页面加载即可</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/88d8e95cbbe78cb93e8c43f00cf92f57.png" alt="image-20200630114914779"></p>
<p><strong>将项目克隆到本地</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/ecd4d35e1eac4e6a71efe1089f855fbd.png" alt="image-20200630115427594"></p>
<figure class="highlight bash"><table><tr><td class="code"><pre><span class="line"><span class="comment">#git clone 码云上的项目地址</span></span><br><span class="line">git <span class="built_in">clone</span> https://gitee.com/crow_678/JavaGuide.git</span><br></pre></td></tr></table></figure>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/10b6c23c7bbcfddebbd608468a2754ff.png" alt="image-20200630115535023"></p>
<p><strong>速度还行</strong></p>
<p><strong>当我们导入一个比较大的项目时</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/71747e5f946516ec19148fcfd9003832.png" alt="image-20200630120819524"></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/e702ecef3ef4897a5a88f509587c1494.png" alt="image-20200630121226310"></p>
<h2 id="2-使用在线的网站"><a href="#2-使用在线的网站" class="headerlink" title="2.使用在线的网站"></a>2.使用在线的网站</h2><p><a href="http://g.widyun.com/" target="_blank" rel="noopener">http://g.widyun.com/</a></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/7aa20b8396ecd033331e7199c956bd3f.png" alt="image-20200630121331482"></p>
<p><strong>复制项目网址到中间的输入框,点击获取连接耐心等待</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/b7cdf7a2b2fb2ccbb03901b77a6352ce.png" alt="image-20200630122021103"></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/30/62fcf183c409d8fb19fae2201204522a.png" alt="image-20200630122104574"></p>
<h2 id="1-仓库名称"><a href="#1-仓库名称" class="headerlink" title="1.仓库名称"></a>1.仓库名称</h2><ul>
<li>springboot stars大于3000的项目并且fork>4000<blockquote>
<p>in:name springboot stars:>3000 forks:>4000<br>in:name 项目名称 stars:数量 forks:数量</p>
</blockquote>
</li>
</ul>
<h2 id="2-Readme-md文件"><a href="#2-Readme-md文件" class="headerlink" title="2.Readme.md文件"></a>2.Readme.md文件</h2><ul>
<li>springboot stars大于3000的项目并且fork>4000<blockquote>
<p>in:readme spring boot stars:>3000 forks:>4000<br>in:readme 项目名称 stars:数量 forks:数量</p>
</blockquote>
</li>
</ul>
<h2 id="3-描述文件"><a href="#3-描述文件" class="headerlink" title="3.描述文件"></a>3.描述文件</h2><ul>
<li>微服务项目 stars>1000 语言为java 最后一次更新时间再2019-09-01之后<blockquote>
<p>in:description 微服务 stars:>1000 language:java pushed:>2019-09-01<br>in:description 项目名称 stars:数量 forks:数量 language:编程语言 pushed:更新时间</p>
</blockquote>
</li>
</ul>
<p>in:description 项目名称 stars:数量 forks:数量 language:编程语言 pushed:更新时间</p>
<p><strong>Github官方使用文档</strong><br><a href="https://help.github.com/en/github/searching-for-information-on-github/searching-for-repositories" target="_blank" rel="noopener">https://help.github.com/en/github/searching-for-information-on-github/searching-for-repositories</a></p>
]]></content>
<categories>
<category>生产力</category>
</categories>
<tags>
<tag>Github</tag>
</tags>
</entry>
<entry>
<title>C语言程序设计概述</title>
<url>/posts/c5a3/</url>
<content><![CDATA[<h1 id="C语言程序设计概述"><a href="#C语言程序设计概述" class="headerlink" title="C语言程序设计概述"></a>C语言程序设计概述</h1><h2 id="1-C语言的发展历程"><a href="#1-C语言的发展历程" class="headerlink" title="1.C语言的发展历程"></a>1.C语言的发展历程</h2><ul>
<li>1.为什么发明C语言：C语言的诞生是和UNIX操作系统的开发密不可分的，原先的UNⅨX操作系统都是用汇编语言写的，1973年UNIX操作系统的核心用C语言改写，从此以后，C语言成为编写操作系统的主要语言</li>
<li>2.C语言对其它语言的影响：很多编程语言都深受C语言的影响，比如C艹（原先是C语言的一个扩展）、C#、 Java、PHP、 Javascript、Perl、LPC和UNIX的 C Shell等</li>
<li>掌握C语言的人，再学其它编程语言，大多能很快上手，触类旁通，很多大学将C语言作为计算机教学的入门</li>
<li>C语言之父 <strong>丹尼斯·麦卡利斯泰尔·里奇</strong>（英语：<strong>Dennis MacAlistair Ritchie</strong></li>
</ul>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn/img/20200703203727.png" alt="1-15030119511M02"></p>
<p><strong>程序：</strong></p>
<ul>
<li>为了<code>计算机</code><strong>执行某些操作或解决某个问题</strong>而编写的一系列<strong>有序指令的集合</strong></li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="comment">//引入头文件</span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio h></span></span></span><br><span class="line"><span class="comment">//main函数，是程序的执行入口，即程序是从main函数开始执行</span></span><br><span class="line"><span class="comment">//void表示main函数没有返回值</span></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="comment">//函数体</span></span><br><span class="line"> <span class="comment">//printf是一个函数，需要是一个头文件才能使用</span></span><br><span class="line"> <span class="comment">//printf是在< stdio. h>，需要引入该头文件</span></span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"hello, world!"</span>);</span><br><span class="line"> <span class="comment">//让窗口停留</span></span><br><span class="line"> getchar;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h2 id="2-C语言的特点"><a href="#2-C语言的特点" class="headerlink" title="2.C语言的特点"></a>2.C语言的特点</h2><ul>
<li>代码级别的<strong>跨平台</strong>：由于标准的存在，使得几乎同样的C代码可用于多种操作系统，如 Windows、DOS、UNIX等等；也适用于多种机型。</li>
<li><strong>允许直接访问物理地址</strong>，<strong>对硬件进行操作</strong> 因此它<strong>既具有高级语言的功能</strong>，<strong>又具有低级语言的许多功能</strong>，C语言可用来写系统软件（比如操作系统，数据库，杀毒软件，防火墙，驱动，服务器程序）。</li>
<li>C语言是一个有<strong>结构化程序设计</strong>、具有<strong>变量作用域（ variable scope）</strong>以及<strong>递归功能</strong>的过程式语言</li>
<li>C语言<code>传递参数</code>可以是<code>值传递</code>（ pass by value，值），也可以<code>传递指针</code>（ a pointer passed by value，地址）也叫<code>引用传递</code></li>
<li>C语言中，没有对象，不同的变量类型可以用结构体（ struct）组合在一起</li>
<li>预编译处理（ preprocessor），生成目标代码质量高，程序执行效率高</li>
</ul>
<h2 id="3-C语言运行机制"><a href="#3-C语言运行机制" class="headerlink" title="3.C语言运行机制"></a>3.C语言运行机制</h2><p><strong>C程序运行机制过程</strong></p>
<ul>
<li><p>1.编辑：比如编写我们的 hello. c文件，就是<code>源代码</code>,</p>
</li>
<li><p>2.编译：将 <code>hello.c</code>程序通过编译器将其编译成<code>目标文件(hell.obj)</code>在<strong>计算机底层</strong>执行</p>
</li>
<li><p>3.链接：将目标文件 hello. obj + <code>库文件</code>生成可执行文件(My ProjectoR.exe)<strong>计算机底层</strong>执行</p>
<p>链接库文件的原因：我们的C程序中会使用<code>C程序库</code>的内容，比如< stdio.h>< stdlib. h>中的函数printf system（）等等，这些函数不是程序员自己写的，而是C程序库中提供的,</p>
<p>链接链接后，生成的exe文件，会比obj文件更大</p>
</li>
<li><p>4.运行：执行<code>exe</code>文件，得到运行结果</p>
<p> <strong>运行机制图解</strong></p>
</li>
</ul>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn/img/20200704093956.png" alt="image-20200704093722914"></p>
<h2 id="4-转义字符"><a href="#4-转义字符" class="headerlink" title="4.转义字符"></a>4.转义字符</h2><table>
<thead>
<tr>
<th>转义字符</th>
<th>含义</th>
</tr>
</thead>
<tbody><tr>
<td>\t</td>
<td>一个制表符,用于格式对齐</td>
</tr>
<tr>
<td>\n</td>
<td>换行符</td>
</tr>
<tr>
<td>\\</td>
<td>表示一个\反斜杠</td>
</tr>
<tr>
<td>\“</td>
<td>表示一个”</td>
</tr>
<tr>
<td>\‘</td>
<td>表示一个’</td>
</tr>
<tr>
<td>\r</td>
<td>表示回车</td>
</tr>
</tbody></table>
<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><div class="btn-center">
<a class="btn-beautify button--animated outline green larger" href="https://www.bilibili.com/video/BV1qJ411z7Hf?p=4" target="_blank" rel="noopener" title="尚硅谷C语言入门"><i class="far fa-hand-point-right fa-fw"></i> 尚硅谷C语言入门 </a>
<a class="btn-beautify button--animated outline green larger" href="https://www.runoob.com/cprogramming/c-standard-library.html" target="_blank" rel="noopener" title="C语言标准库参考手册"><i class="far fa-hand-point-right fa-fw"></i> C语言标准库参考手册 </a>
</div>]]></content>
<categories>
<category>C</category>
</categories>
<tags>
<tag>C</tag>
</tags>
</entry>
<entry>
<title>IDEA快捷键</title>
<url>/posts/aa80/</url>
<content><![CDATA[<h2 id="断点调试"><a href="#断点调试" class="headerlink" title="断点调试"></a>断点调试</h2><p><a href="https://www.cnblogs.com/xiemingjun/p/9618427.html" target="_blank" rel="noopener">https://www.cnblogs.com/xiemingjun/p/9618427.html</a></p>
]]></content>
<categories>
<category>生产力</category>
</categories>
<tags>
<tag>IDEA</tag>
</tags>
</entry>
<entry>
<title>Java面向对象的三大特性</title>
<url>/posts/9d0/</url>
<content><![CDATA[<h2 id="封装"><a href="#封装" class="headerlink" title="封装"></a>封装</h2><ul>
<li>参考链接</li>
<li><a href="https://www.cnblogs.com/chenssy/p/3351835.html" target="_blank" rel="noopener">https://www.cnblogs.com/chenssy/p/3351835.html</a></li>
</ul>
<h2 id="继承"><a href="#继承" class="headerlink" title="继承"></a>继承</h2><ul>
<li>参考链接</li>
<li><a href="https://www.cnblogs.com/chenssy/p/3354884.html" target="_blank" rel="noopener">https://www.cnblogs.com/chenssy/p/3354884.html</a></li>
</ul>
<p>##多态</p>
<ul>
<li>参考链接</li>
<li><a href="https://www.cnblogs.com/chenssy/p/3372798.html" target="_blank" rel="noopener">https://www.cnblogs.com/chenssy/p/3372798.html</a></li>
</ul>
]]></content>
<categories>
<category>Java</category>
</categories>
<tags>
<tag>面向对象</tag>
<tag>Java</tag>
</tags>
</entry>
<entry>
<title>C语言易错点</title>
<url>/posts/9db8/</url>
<content><![CDATA[<h2 id="语法基础"><a href="#语法基础" class="headerlink" title="语法基础"></a>语法基础</h2><ul>
<li><p><strong>getchar()函数</strong>从终端读取一个字符（一次只读取一个字符）并将其作为整数返回</p>
</li>
<li><p><strong>所有C语句必须以分号结尾。</strong></p>
</li>
</ul>
<p><strong>C语言关键字</strong></p>
<table>
<thead>
<tr>
<th>关键字</th>
<th>说明</th>
</tr>
</thead>
<tbody><tr>
<td>auto</td>
<td>声明自动变量</td>
</tr>
<tr>
<td>short</td>
<td>声明短整型变量或函数</td>
</tr>
<tr>
<td>int</td>
<td>声明整型变量或函数</td>
</tr>
<tr>
<td>long</td>
<td>声明长整型变量或函数</td>
</tr>
<tr>
<td>float</td>
<td>声明浮点型变量或函数</td>
</tr>
<tr>
<td>double</td>
<td>声明双精度变量或函数</td>
</tr>
<tr>
<td>char</td>
<td>声明字符型变量或函数</td>
</tr>
<tr>
<td>struct</td>
<td>声明结构体变量或函数</td>
</tr>
<tr>
<td><strong>union</strong></td>
<td><strong>声明共用数据类型</strong></td>
</tr>
<tr>
<td>enum</td>
<td>声明枚举类型</td>
</tr>
<tr>
<td><strong>typedef</strong></td>
<td><strong>用以给数据类型取别名</strong></td>
</tr>
<tr>
<td>const</td>
<td>声明只读变量</td>
</tr>
<tr>
<td>unsigned</td>
<td>声明无符号类型变量或函数</td>
</tr>
<tr>
<td>signed</td>
<td>声明有符号类型变量或函数</td>
</tr>
<tr>
<td>extern</td>
<td>声明变量是在其他文件正声明</td>
</tr>
<tr>
<td><strong>register</strong></td>
<td><strong>声明寄存器变量</strong></td>
</tr>
<tr>
<td>static</td>
<td>声明静态变量</td>
</tr>
<tr>
<td>volatile</td>
<td>说明变量在程序执行中可被隐含地改变</td>
</tr>
<tr>
<td>void</td>
<td>声明函数无返回值或无参数，声明无类型指针</td>
</tr>
<tr>
<td>if</td>
<td>条件语句</td>
</tr>
<tr>
<td>else</td>
<td>条件语句否定分支（与 if 连用）</td>
</tr>
<tr>
<td>switch</td>
<td>用于开关语句</td>
</tr>
<tr>
<td>case</td>
<td>开关语句分支</td>
</tr>
<tr>
<td>for</td>
<td>一种循环语句</td>
</tr>
<tr>
<td>do</td>
<td>循环语句的循环体</td>
</tr>
<tr>
<td>while</td>
<td>循环语句的循环条件</td>
</tr>
<tr>
<td>goto</td>
<td>无条件跳转语句</td>
</tr>
<tr>
<td>continue</td>
<td>结束当前循环，开始下一轮循环</td>
</tr>
<tr>
<td>break</td>
<td>跳出当前循环</td>
</tr>
<tr>
<td>default</td>
<td>开关语句中的“其他”分支</td>
</tr>
<tr>
<td>sizeof</td>
<td>计算数据类型长度</td>
</tr>
<tr>
<td>return</td>
<td>子程序返回语句（可以带参数，也可不带参数）循环条件</td>
</tr>
</tbody></table>
<ul>
<li><p><strong>实型数据也称为浮点数或实数</strong></p>
</li>
<li><p><code>int</code>C语言中数据类型的合法值范围是-32768-32767</p>
</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line">main()</span><br><span class="line">{</span><br><span class="line"> <span class="keyword">int</span> i = <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> j = <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">switch</span>(i)</span><br><span class="line"> {</span><br><span class="line"> <span class="keyword">case</span> <span class="number">1</span>: <span class="built_in">printf</span>(<span class="string">"one"</span>);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> <span class="keyword">case</span> j: <span class="built_in">printf</span>(<span class="string">"two"</span>);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> } </span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>错误，常量表达式需要代替j。将j改为2</strong></p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="built_in">printf</span>(<span class="number">5</span> + <span class="string">"Good Morning"</span>);</span><br><span class="line"><span class="comment">//Good Morning</span></span><br></pre></td></tr></table></figure>
<p><strong>跳过后面的字符串的5个字符，然后打印字符串。</strong></p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line">main()</span><br><span class="line">{</span><br><span class="line"> <span class="keyword">int</span> a =<span class="number">10</span>;</span><br><span class="line"> <span class="keyword">if</span>(a = <span class="number">5</span>)</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"hello"</span>);</span><br><span class="line"> <span class="keyword">else</span></span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"bye"</span>);</span><br><span class="line">}</span><br><span class="line"><span class="comment">//a=5 赋值操作 输出hello</span></span><br></pre></td></tr></table></figure>
<p><strong>union的大小由最大的成员的大小决定；</strong></p>
<h2 id="指针"><a href="#指针" class="headerlink" title="指针"></a>指针</h2><p><strong>如果变量是指向结构的指针，那么以下哪个运算符用于通过指针变量访问结构的数据成员？</strong></p>
<p><code>-></code></p>
<p><strong>用于访问变量值的运算符在指针变量中存储的地址是？</strong></p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="keyword">int</span> num = <span class="number">100</span>;</span><br><span class="line"> <span class="keyword">int</span>* ptr = &num;</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"ptr本身的地址=%p ptr存放的地址=%p ptr指向的值"</span>,&ptr,ptr,*ptr);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h2 id="结构体"><a href="#结构体" class="headerlink" title="结构体"></a>结构体</h2><p><strong>结构体初始化问题</strong></p>
<p><strong>通过结构体指针访问结构体的变量</strong></p>
<p>1.当结构体内使用字符型的指针<code>char*</code>时</p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span></span></span><br><span class="line"><span class="class"> {</span></span><br><span class="line"> <span class="keyword">int</span> age;</span><br><span class="line"> <span class="keyword">char</span> *name;</span><br><span class="line"> };</span><br></pre></td></tr></table></figure>
<ul>
<li>结构体初始化</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span> <span class="title">str</span> = {</span><span class="number">1</span>,<span class="string">"test1"</span>};</span><br></pre></td></tr></table></figure>
<ul>
<li>创建结构体指针</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span> *<span class="title">s</span> = <span class="title">NULL</span>;</span></span><br></pre></td></tr></table></figure>
<ul>
<li>让指针指向结构体</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line">s = &str;</span><br></pre></td></tr></table></figure>
<ul>
<li>通过结构体指针访问结构体的成员变量</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="built_in">printf</span>(<span class="string">"name:%s\n"</span>,(*s).name);</span><br><span class="line"><span class="built_in">printf</span>(<span class="string">"age:%d\n"</span>,(*s).age);</span><br></pre></td></tr></table></figure>
<p>2.当结构体内使用字符型数组<code>char[]</code>时</p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span></span></span><br><span class="line"><span class="class"> {</span></span><br><span class="line"> <span class="keyword">int</span> age;</span><br><span class="line"> <span class="comment">//注意字符数组的初始化</span></span><br><span class="line"> <span class="keyword">char</span> name[<span class="number">20</span>];</span><br><span class="line"> };</span><br></pre></td></tr></table></figure>
<ul>
<li>结构体初始化</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span> <span class="title">str</span>;</span></span><br><span class="line">str.age = <span class="number">100</span>;</span><br><span class="line">str.name = <span class="string">"test"</span>;</span><br></pre></td></tr></table></figure>
<ul>
<li>让结构体指针指向结构体</li>
<li>通过结构体指针访问结构体变量的代码与前面相同</li>
</ul>
<p><strong>结构体初始化错误方式</strong></p>
<ul>
<li>字符数组未初始化 会导致栈溢出</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span></span></span><br><span class="line"><span class="class"> {</span></span><br><span class="line"> <span class="keyword">int</span> age;</span><br><span class="line"> <span class="keyword">char</span> name[];</span><br><span class="line"> };</span><br></pre></td></tr></table></figure>
<ul>
<li>先声明结构体后,一次性初始化结构体全部成员变量</li>
</ul>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">std</span> <span class="title">str</span>;</span></span><br><span class="line">str = {<span class="number">1</span>,<span class="string">"test"</span>};</span><br></pre></td></tr></table></figure>
<p><strong>全部代码如下</strong></p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><string.h></span></span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="class"><span class="keyword">struct</span> <span class="title">std</span></span></span><br><span class="line"><span class="class"> {</span></span><br><span class="line"> <span class="keyword">int</span> age;</span><br><span class="line"> <span class="keyword">char</span> *name;</span><br><span class="line"> };</span><br><span class="line"> <span class="comment">//struct std str = {1,"test1"};</span></span><br><span class="line"> <span class="class"><span class="keyword">struct</span> <span class="title">std</span> <span class="title">str</span>;</span></span><br><span class="line"> str.age = <span class="number">100</span>;</span><br><span class="line"> str.name = <span class="string">"test"</span>;</span><br><span class="line"> <span class="class"><span class="keyword">struct</span> <span class="title">std</span> *<span class="title">s</span> = <span class="title">NULL</span>;</span></span><br><span class="line"> s = &str;</span><br><span class="line"> <span class="comment">//strcpy((*s).name,"test");</span></span><br><span class="line"> <span class="comment">//(*s).age = 100;</span></span><br><span class="line"> <span class="comment">//str.name = "test";</span></span><br><span class="line"></span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"name:%s\n"</span>,(*s).name);</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"age:%d\n"</span>,(*s).age);</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
]]></content>
<categories>
<category>C</category>
</categories>
<tags>
<tag>C</tag>
</tags>
</entry>
<entry>
<title>MyBatis</title>
<url>/posts/f1de/</url>
<content><![CDATA[]]></content>
<categories>
<category>后端框架</category>
</categories>
<tags>
<tag>MyBatis</tag>
</tags>
</entry>
<entry>
<title>Java集合</title>
<url>/posts/5257/</url>
<content><![CDATA[<h1 id="集合分类："><a href="#集合分类：" class="headerlink" title="集合分类："></a>集合分类：</h1><p><strong>List,Set,Map三者的区别</strong></p>
<p><strong>List(顺序)</strong>： List接⼝存储⼀组不唯⼀（可以有<strong>多个元素引⽤相同的对象</strong>），<strong>有序</strong>的对象</p>
<p><strong>Set(不重复):</strong> 不允许重复的集合。<strong>不会有多个元素引⽤相同的对象。</strong></p>
<p><strong>Map(键Key):</strong> 使⽤<code>键值对</code>存储。Map会维护与Key有关联的值。<strong>两个Key可以引⽤相</strong></p>
<p><strong>同的对象</strong>，但Key不能重复，典型的Key是String类型，但也可以是任何对象。</p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn/img/20200703152229.png" alt="image-20200703152225014"></p>
<h2 id="List"><a href="#List" class="headerlink" title="List"></a>List</h2><h3 id="1-1ArrayList"><a href="#1-1ArrayList" class="headerlink" title="1.1ArrayList"></a>1.1ArrayList</h3><p><code>ArrayList</code>实现了<strong>长度可变的数组</strong>,数组<strong>元素类型为Object类型</strong>,即<strong>可以存放所有类型数据</strong>,内存中<strong>分配连续的空间</strong>。</p>
<ul>
<li><p><strong>遍历元素</strong>和<strong>随机访问元素</strong>的效率比较高 </p>
</li>
<li><p>构造ArrayList时；若使用<strong>默认构造函数</strong>，则ArrayList的<strong>默认容量大小是10。</strong></p>
</li>
<li><p>ArrayList<strong>容量不足以容纳全部元素</strong>时，ArrayList会<strong>重新设置容量</strong>：<strong>新的容量=“(原始容量x3)/2 + 1”。</strong></p>
</li>
<li><p>ArrayList实现``java.io.Serializable`的方式。当<strong>写入到输出流</strong>时，<strong>先写入“容量”</strong>，<strong>再依次写入“每一个元素”</strong>；当<strong>读出输入流</strong>时，<strong>先读取“容量”，再依次读取“每一个元素</strong></p>
</li>
</ul>
<p> <strong>内存图解</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn/img/20200703180004.png" alt="image-20200703154835792"></p>
<p><code>ArrayList</code>的常用方法</p>
<p><strong>增加</strong></p>
<ul>
<li><p><code>add();</code> 加入一个元素（Object）</p>
</li>
<li><p><code>addAll();</code> 加入集合元素（Collection）</p>
</li>
<li><p><code>add(index, element);</code>在指定位置添加元素></p>
</li>
</ul>
<p><strong>删除</strong></p>
<ul>
<li><code>remove(int index)</code> 通过索引删除<strong>指定位置</strong>的元素。 </li>
<li><code>remove(Object o)</code> 删除第一次出现的指定元素从这个列表,如果它存在。 </li>
</ul>
<p>注意重载</p>
<ul>
<li><code>removeAll(Collection c)</code> 从这个列表中移除所有元素包含在指定的集合</li>
</ul>
<p><strong>修改</strong></p>
<ul>
<li><code>set(index, element)</code> 取代<strong>指定位置</strong>上的元素</li>
</ul>
<p><strong>查询</strong></p>
<ul>
<li><p><code>size()</code> 查看<strong>集合的长度</strong>:</p>
</li>
<li><p><code>indexOf()</code> 通过索引查询指定元素 <strong>从前往后查</strong></p>
</li>
<li><p><code>lastIndexOf()</code> 通过索引查询指定元素,<strong>从后向前查找</strong></p>
</li>
<li><p><code>contains()</code> 判读集合中<strong>是否包含某个元素</strong></p>
</li>
</ul>
<p><strong>其他方法</strong></p>
<ul>
<li><code>subList(start, end)</code> 截取集合内的元素 （起始索引,结束索引）</li>
</ul>
<p><strong>遍历</strong></p>
<ul>
<li>for循环</li>
</ul>
<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">for</span>(<span class="keyword">int</span> i = <span class="number">0</span>; i < arrayList.size(); i++) {</span><br><span class="line"> System.out.println(arrayList.get(i));</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<ul>
<li>foreach循环</li>
</ul>
<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">for</span>(Object o:arrayList) {</span><br><span class="line"> System.out.println(o);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<ul>
<li>迭代器<code>Iterator</code></li>
</ul>
<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">Iterator iterator = arrayList.iterator();</span><br><span class="line"> <span class="keyword">while</span>(iterator.hasNext()) {</span><br><span class="line"> System.out.println(iterator.next());</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>遍历ArrayList时，使用随机访问 (通过索引序号访问) 效率最高，而使用迭代器的效率最低</strong></p>
<p>🔗参考链接</p>
<ul>
<li><a href="https://blog.csdn.net/qq_43776742/article/details/91042479" target="_blank" rel="noopener">https://blog.csdn.net/qq_43776742/article/details/91042479</a></li>
</ul>
]]></content>
<categories>
<category>Java</category>
</categories>
<tags>
<tag>Java</tag>
<tag>集合</tag>
</tags>
</entry>
<entry>
<title>KMP算法</title>
<url>/posts/8c51/</url>
<content><![CDATA[<p>KMP算法的应用场景是字符串匹配</p>
<p><strong>问题描述</strong></p>
<blockquote>
<p>有一个字符串 str1= “BBC ABCDAB ABCDABCDABDE”，和一个子串 str2=”ABCDABD”,</p>
<p>现在要判断str1是否含有str2, 如果存在，就返回第一次出现的位置, 如果没有，则返回-1</p>
</blockquote>
<h2 id="暴力破解"><a href="#暴力破解" class="headerlink" title="暴力破解"></a>暴力破解</h2><ul>
<li>将两个字符串分别存入两个字符数组中分别为c1,和c2</li>
</ul>
<p>BBC ABCDAB ABCDABCDABDE</p>
<p><strong>ABCDABD</strong></p>
<p>思路</p>
<p>两个辅助变量为S和T</p>
<p>一个字符一个字符进行匹配，相同时S和T均向后移动一位，直到字符串末尾，不能匹配时，将S移动到</p>
<h2 id="KMP算法"><a href="#KMP算法" class="headerlink" title="KMP算法"></a>KMP算法</h2><p>字符串不进行回溯，移动字串</p>
<p>根据子串编写部分匹配表</p>
<p>编写规则</p>
<p><strong>ABCDABD</strong></p>
<table>
<thead>
<tr>
<th>子串的字符</th>
<th>前缀</th>
<th>后缀</th>
<th>前缀与后缀的最大公共字符数</th>
</tr>
</thead>
<tbody><tr>
<td>A</td>
<td>无</td>
<td>无</td>
<td>0</td>
</tr>
<tr>
<td>AB</td>
<td>A</td>
<td>B</td>
<td>0</td>
</tr>
<tr>
<td>ABC</td>
<td>A,AB</td>
<td>BC,C</td>
<td>0</td>
</tr>
<tr>
<td>ABCD</td>
<td>A,AB,ABC</td>
<td>BCD,CD,D</td>
<td>0</td>
</tr>
<tr>
<td>ABCDA</td>
<td>A,AB,ABC,ABCD</td>
<td>BCDA,CDA,CD,A</td>
<td>1</td>
</tr>
<tr>
<td>ABCDAB</td>
<td>A,AB,ABC,ABCD,ABCDA</td>
<td>BCDAB,CDAB,DAB,AB,B</td>
<td>2</td>
</tr>
</tbody></table>
<p><strong>移动位数 = 以匹配的字符数 - 前缀与后缀的最大公共字符数</strong></p>
]]></content>
<categories>
<category>数据结构和算法</category>
</categories>
<tags>
<tag>C++</tag>
<tag>KMP</tag>
<tag>算法</tag>
</tags>
</entry>
<entry>
<title>make和makefile文件</title>
<url>/posts/bfbe/</url>
<content><![CDATA[<p>make</p>
<p>用处：用来管理多模块程序的的编译和链接，直至生成可执行文件</p>
<p>Clion分模块编译</p>
<p>1.最外层的CmakeLists</p>
<figure class="highlight cmake"><table><tr><td class="code"><pre><span class="line"><span class="keyword">cmake_minimum_required</span>(VERSION <span class="number">3.17</span>)</span><br><span class="line"><span class="keyword">project</span>(Game C)</span><br><span class="line"></span><br><span class="line"><span class="keyword">set</span>(CMAKE_C_STANDARD <span class="number">99</span>)</span><br><span class="line"></span><br><span class="line"><span class="keyword">add_subdirectory</span>(code/Bird)</span><br><span class="line"><span class="keyword">add_subdirectory</span>(code/Triangle)</span><br><span class="line"><span class="keyword">add_subdirectory</span>(code/public)</span><br></pre></td></tr></table></figure>
<p>2.内层CmakeLists</p>
<figure class="highlight cmake"><table><tr><td class="code"><pre><span class="line"><span class="keyword">add_subdirectory</span>(Bird)</span><br><span class="line"><span class="keyword">add_subdirectory</span>(Triangle)</span><br><span class="line"><span class="keyword">add_subdirectory</span>(public)</span><br></pre></td></tr></table></figure>
<p>3.最内层CmakeLists</p>
<figure class="highlight cmake"><table><tr><td class="code"><pre><span class="line"><span class="comment"># 包含公共库</span></span><br><span class="line"><span class="keyword">include_directories</span>(<span class="variable">${CMAKE_SOURCE_DIR}</span>/code/public)</span><br><span class="line"></span><br><span class="line"><span class="comment"># 生成可执行文件</span></span><br><span class="line"><span class="keyword">add_executable</span>(Bird Bird.c)</span><br><span class="line"><span class="comment"># 链接公共库</span></span><br><span class="line"><span class="keyword">target_link_libraries</span>(Bird Scanf_lib)</span><br></pre></td></tr></table></figure>
<figure class="highlight cmake"><table><tr><td class="code"><pre><span class="line"><span class="comment"># 生成一个静态库，因为所有其他数据结构都会引用这个库</span></span><br><span class="line"><span class="keyword">add_library</span>(Scanf_lib public.c)</span><br></pre></td></tr></table></figure>
]]></content>
<categories>
<category>uncategorized</category>
</categories>
<tags>
<tag>make</tag>
<tag>makefile</tag>
</tags>
</entry>
<entry>
<title>Nginx配置SSL证书</title>
<url>/posts/27ab/</url>
<content><![CDATA[<blockquote>
<p>环境</p>
</blockquote>
<ul>
<li>阿里云 centos7.7</li>
<li>SSL证书</li>
<li>Nginx/1.17.9</li>
<li>一个解析好的域名</li>
<li>Xshell 和 Xftp</li>
</ul>
<p><strong>Nginx安装SSL官网文档:</strong><br><a href="https://help.aliyun.com/document_detail/98728.html?spm=5176.2020520163.0.0.113156a7LfBJvD" target="_blank" rel="noopener">https://help.aliyun.com/document_detail/98728.html?spm=5176.2020520163.0.0.113156a7LfBJvD</a></p>
<p><strong>开始配置</strong></p>
<ul>
<li>在Nginx安装目录（默认Nginx安装目录为/usr/local/nginx/conf）下创建cert目录，并将下载的证书文件和密钥文件拷贝到cert目录中。</li>
</ul>
<p><img src= "/img/loading.gif" data-src="https://i.loli.net/2020/04/30/YEZrqlSAVxCwpFG.png" alt="image.png"></p>
<p><strong>编辑nginx配置文件</strong></p>
<figure class="highlight bash"><table><tr><td class="code"><pre><span class="line"><span class="comment"># HTTPS server</span></span><br><span class="line"> server {</span><br><span class="line"> listen 443 ssl;</span><br><span class="line"> server_name www.crow1024.top;</span><br><span class="line"> </span><br><span class="line"> ssl_certificate cert/3816266_www.crow1024.top.pem;</span><br><span class="line"> ssl_certificate_key cert/3816266_www.crow1024.top.key;</span><br><span class="line"> </span><br><span class="line"> ssl_session_cache shared:SSL:1m;</span><br><span class="line"> ssl_session_timeout 5m;</span><br><span class="line"> </span><br><span class="line"> ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE:ECDH:AES:HIGH:!NULL:!aNULL:!MD5:!ADH:!RC4;</span><br><span class="line"> ssl_protocols TLSv1 TLSv1.1 TLSv1.2;</span><br><span class="line"> ssl_prefer_server_ciphers on;</span><br><span class="line"> </span><br><span class="line"> location / {</span><br><span class="line"> root html;</span><br><span class="line"> proxy_set_header HOST <span class="variable">$host</span>;</span><br><span class="line"> proxy_set_header X-Forwarded-Proto <span class="variable">$scheme</span>;</span><br><span class="line"> proxy_set_header X-Real-IP <span class="variable">$remote_addr</span>;</span><br><span class="line"> proxy_set_header X-Forwarded-For <span class="variable">$proxy_add_x_forwarded_for</span>; </span><br><span class="line"> proxy_pass http://127.0.0.1:8090;</span><br><span class="line"> index index.html index.htm;</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p><strong>location中注意点</strong></p>
<ul>
<li>http后面没有s</li>
<li>加上halo的默认端口号<br><img src= "/img/loading.gif" data-src="https://i.loli.net/2020/04/30/GYWplMZtP9eNrQH.png" alt="image.png"></li>
</ul>
<p><strong>保存退出切换到sbin目录下</strong></p>
<figure class="highlight bash"><table><tr><td class="code"><pre><span class="line">[root@crow ~]<span class="comment"># cd /usr/local/nginx/sbin</span></span><br><span class="line"><span class="comment"># 停止nginx服务</span></span><br><span class="line">./nginx -s stop</span><br><span class="line"><span class="comment"># 启动nginx</span></span><br><span class="line">./nginx</span><br></pre></td></tr></table></figure>
<p><strong>打开浏览器就可以直接通过域名访问</strong></p>
]]></content>
<categories>
<category>服务器</category>
</categories>
<tags>
<tag>服务器</tag>
</tags>
</entry>
<entry>
<title>内存分区模型</title>
<url>/posts/a132/</url>
<content><![CDATA[<p>C++程序在执行时，将内存大方向划分为<strong>4个区域</strong></p>
<ul>
<li><code>代码区</code>：存放函数体的<strong>二进制代码</strong>，由<strong>操作系统进行管理</strong></li>
<li><code>全局区</code>：存放<strong>全局变量</strong>和<strong>静态变量</strong>以及<strong>常量</strong></li>
<li><code>栈区</code>：<strong>编译器自动分配释放</strong>, 存放<strong>函数的参数值</strong>,<strong>局部变量</strong>等</li>
<li><code>堆区</code>：<strong>手动分配和释放,没有手动释放</strong>,程序结束时<strong>由操作系统回收</strong></li>
</ul>
<p><strong>内存四区意义：</strong></p>
<p><strong>不同区域存放的数据，赋予不同的生命周期</strong>, 便于开发程序</p>
<h2 id="程序运行前"><a href="#程序运行前" class="headerlink" title="程序运行前"></a>程序运行前</h2><p>程序编译后，生成了exe可执行程序，<strong>未执行该程序前</strong>分为<strong>两个区域</strong></p>
<p><strong>代码区：</strong></p>
<ul>
<li>存放 CPU 执行的<strong>机器指令(二进制代码)</strong></li>
<li>代码区是<strong>共享</strong>的，共享的目的是<strong>对于频繁被执行的程序，内存中有一份代码即可</strong></li>
<li>代码区是<strong>只读</strong>的，使其只读的原因是<strong>防止程序意外地修改了它的指令</strong></li>
</ul>
<p><strong>全局区：</strong></p>
<ul>
<li><code>全局变量</code>和<code>静态变量</code>存放位置</li>
<li>全局区还包含了<code>常量区</code>, <code>字符串常量</code>和<code>其他常量</code>也存放在此.</li>
<li><strong>该区域的数据在程序结束后由操作系统释放</strong></li>
</ul>
<p><strong>🌰举例：</strong></p>
<figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><iostream></span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="built_in">std</span>;</span><br><span class="line"><span class="comment">//全局变量</span></span><br><span class="line"><span class="keyword">int</span> g_a = <span class="number">10</span>;</span><br><span class="line"><span class="keyword">int</span> g_b = <span class="number">10</span>;</span><br><span class="line"></span><br><span class="line"><span class="comment">//全局常量</span></span><br><span class="line"><span class="keyword">const</span> <span class="keyword">int</span> c_g_a = <span class="number">10</span>;</span><br><span class="line"><span class="keyword">const</span> <span class="keyword">int</span> c_g_b = <span class="number">10</span>;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="comment">//局部变量</span></span><br><span class="line"> <span class="keyword">int</span> a = <span class="number">10</span>;</span><br><span class="line"> <span class="keyword">int</span> b = <span class="number">10</span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//打印地址</span></span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"局部变量a地址为： "</span> << &a << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"局部变量b地址为： "</span> << &b << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"全局变量g_a地址为： "</span> << &g_a << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"全局变量g_b地址为： "</span> << &g_b << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//静态变量</span></span><br><span class="line"> <span class="keyword">static</span> <span class="keyword">int</span> s_a = <span class="number">10</span>;</span><br><span class="line"> <span class="keyword">static</span> <span class="keyword">int</span> s_b = <span class="number">10</span>;</span><br><span class="line"></span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"静态变量s_a地址为： "</span> << &s_a << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"静态变量s_b地址为： "</span> << &s_b << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"字符串常量地址为： "</span> << &<span class="string">"hello world"</span> << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"字符串常量地址为： "</span> << &<span class="string">"hello world1"</span> << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"全局常量c_g_a地址为： "</span> << &c_g_a << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"全局常量c_g_b地址为： "</span> << &c_g_b << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">const</span> <span class="keyword">int</span> c_l_a = <span class="number">10</span>;</span><br><span class="line"> <span class="keyword">const</span> <span class="keyword">int</span> c_l_b = <span class="number">10</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"局部常量c_l_a地址为： "</span> << &c_l_a << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"局部常量c_l_b地址为： "</span> << &c_l_b << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> system(<span class="string">"pause"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>打印结果：</strong></p>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">局部变量a地址为： 0x66fe1c</span><br><span class="line">局部变量b地址为： 0x66fe18</span><br><span class="line">全局变量g_a地址为： 0x404010</span><br><span class="line">全局变量g_b地址为： 0x404014</span><br><span class="line">静态变量s_a地址为： 0x404018</span><br><span class="line">静态变量s_b地址为： 0x40401c</span><br><span class="line">字符串常量地址为： 0x405096</span><br><span class="line">字符串常量地址为： 0x4050a2</span><br><span class="line">全局常量c_g_a地址为： 0x405000</span><br><span class="line">全局常量c_g_b地址为： 0x405004</span><br><span class="line">局部常量c_l_a地址为： 0x66fe14</span><br><span class="line">局部常量c_l_b地址为： 0x66fe10</span><br></pre></td></tr></table></figure>
<p><strong>总结：</strong></p>
<ul>
<li>C++中在程序运行前分为<code>全局区</code>和<code>代码区</code></li>
<li><code>代码区</code>特点是<strong>共享和只读</strong></li>
<li><code>全局区</code>中存放<code>全局变量</code>、<code>静态变量</code>、<code>常量</code></li>
<li><code>常量区</code>中存放 <code>const修饰的全局常量</code> 和 <code>字符串常量</code></li>
</ul>
<h2 id="程序运行后"><a href="#程序运行后" class="headerlink" title="程序运行后"></a>程序运行后</h2><p><strong>栈区：</strong></p>
<ul>
<li>编译器<strong>自动分配释放内存</strong>, 存放函数的<code>参数值</code>,<code>局部变量</code>等</li>
<li>注意事项：<strong>不要返回局部变量的地址，栈区开辟的数据由编译器自动释放</strong></li>
</ul>
<p><strong>🌰举例：</strong></p>
<figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">int</span> * <span class="title">func</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">int</span> a = <span class="number">10</span>;</span><br><span class="line"> <span class="keyword">return</span> &a;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> *p = func();</span><br><span class="line"> <span class="comment">//第一次可以打印吃结果的原因:编译器对数据进行了保留</span></span><br><span class="line"> <span class="built_in">cout</span> << *p << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="comment">//再次使用指针在内存中对数据进行操作时,数据已经消失</span></span><br><span class="line"> <span class="built_in">cout</span> << *p << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> system(<span class="string">"pause"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>堆区：</strong></p>
<ul>
<li><strong>手动分配释放</strong>,没有释放,<strong>程序结束时由操作系统回收</strong></li>
<li>C++中主要利用<strong>new在堆区开辟内存</strong></li>
</ul>
<p><strong>🌰举例：</strong></p>
<figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">int</span>* <span class="title">func</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">int</span>* a = <span class="keyword">new</span> <span class="keyword">int</span>(<span class="number">10</span>);</span><br><span class="line"> <span class="keyword">return</span> a;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> *p = func();</span><br><span class="line"></span><br><span class="line"> <span class="built_in">cout</span> << *p << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << *p << <span class="built_in">endl</span>;</span><br><span class="line"> </span><br><span class="line"> system(<span class="string">"pause"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>总结：</strong></p>
<ul>
<li>堆区数据<strong>手动管理开辟和释放</strong></li>
<li>堆区数据利用<strong>new关键字进行开辟内存</strong></li>
</ul>
<h2 id="new操作符"><a href="#new操作符" class="headerlink" title="new操作符"></a>new操作符</h2><ul>
<li>C++中利用<code>new</code>操作符在堆区开辟数据</li>
<li>堆区开辟的数据，由程序员手动开辟，手动释放，释放利用操作符 <code>delete</code></li>
<li>语法：<code>new 数据类型</code></li>
<li><strong>new创建的数据，会返回该数据对应的类型的指针</strong></li>
</ul>
<p><strong>🌰举例：</strong>基本语法</p>
<figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">int</span>* <span class="title">func</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">int</span>* a = <span class="keyword">new</span> <span class="keyword">int</span>(<span class="number">10</span>);</span><br><span class="line"> <span class="keyword">return</span> a;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> *p = func();</span><br><span class="line"></span><br><span class="line"> <span class="built_in">cout</span> << *p << <span class="built_in">endl</span>;</span><br><span class="line"> <span class="built_in">cout</span> << *p << <span class="built_in">endl</span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//利用delete释放堆区数据</span></span><br><span class="line"> <span class="keyword">delete</span> p;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//cout << *p << endl; //报错，释放的空间不可访问</span></span><br><span class="line"></span><br><span class="line"> system(<span class="string">"pause"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><strong>🌰举例：</strong>：开辟数组</p>
<figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="comment">//堆区开辟数组</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span>* arr = <span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">10</span>];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < <span class="number">10</span>; i++)</span><br><span class="line"> {</span><br><span class="line"> arr[i] = i + <span class="number">100</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < <span class="number">10</span>; i++)</span><br><span class="line"> {</span><br><span class="line"> <span class="built_in">cout</span> << arr[i] << <span class="built_in">endl</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">//释放数组 delete 后加 []</span></span><br><span class="line"> <span class="keyword">delete</span>[] arr;</span><br><span class="line"></span><br><span class="line"> system(<span class="string">"pause"</span>);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p> <strong>内存图解</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn/img/20200712201259.png" alt="image-20200712200817949"></p>
<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><div class="btn-center">
<a class="btn-beautify button--animated outline green larger" href="https://www.bilibili.com/video/BV1et411b73Z?p=85" target="_blank" rel="noopener" title="黑马程序员C++教程"><i class="far fa-hand-point-right fa-fw"></i> 黑马程序员C++教程 </a>
</div>
]]></content>
<categories>
<category>C++</category>
</categories>
<tags>
<tag>C++</tag>
<tag>内存分区模型</tag>
</tags>
</entry>
<entry>
<title>十大排序算法</title>
<url>/posts/564c/</url>
<content><![CDATA[<h2 id="插入排序"><a href="#插入排序" class="headerlink" title="插入排序"></a>插入排序</h2><h3 id="直接插入排序"><a href="#直接插入排序" class="headerlink" title="直接插入排序"></a>直接插入排序</h3><p><strong>插入排序法思想</strong>:</p>
<p>把 n 个待排序的元素看成为一个<code>有序表</code>和一个<code>无序表</code>，开始时<strong>有序表中只包含一个元素</strong>，<strong>无序表中包含有 n-1 个元素个元素</strong>，</p>
<p><strong>排序过程</strong></p>
<p>每次从无序表中取出第一个元素，把它的排序码依次与有序表元素的排序码进行比较，将它插入到有序表中的适当位置，使之成为新的有序表。</p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn/img/20200826153417.png" alt="image-20200826152835050"></p>
<ul>
<li>选取数组的第一个元素为基准值，作为有序部分的第一个元素</li>
</ul>
<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">int</span> insertVal = <span class="number">0</span>;</span><br><span class="line"><span class="keyword">int</span> insertIndex = <span class="number">0</span>;</span><br></pre></td></tr></table></figure>
<ul>
<li>遍历寻找无序部分的元素，跟有序部分的元素进行比较，确定元素应该插入的位置</li>
</ul>
<figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="keyword">for</span>(i=<span class="number">1</span>; i<n; i++)</span><br><span class="line"> {</span><br><span class="line"> <span class="comment">//找到要插入的位置</span></span><br><span class="line"> <span class="keyword">for</span>(j=<span class="number">0</span>; j<i; j++)</span><br><span class="line"> {</span><br><span class="line"> ....</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<ul>
<li>插入元素，移动插入位置后的元素</li>
</ul>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line"></span><br><span class="line"></span><br></pre></td></tr></table></figure>
<h3 id="希尔排序"><a href="#希尔排序" class="headerlink" title="希尔排序"></a>希尔排序</h3><figure class="highlight c++"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><iostream></span></span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><vector></span></span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><cstdlib></span></span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><ctime></span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="built_in">std</span>;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">shellSort</span><span class="params">(<span class="built_in">vector</span><<span class="keyword">int</span>>& <span class="built_in">array</span>)</span></span>{</span><br><span class="line"> <span class="comment">//n为数组长度</span></span><br><span class="line"> <span class="keyword">int</span> n = <span class="built_in">array</span>.<span class="built_in">size</span>();</span><br><span class="line"> <span class="comment">//将数组按照步长分为gap个小组，每个小组的第一个数字加上步长得到第二个数字的下标</span></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> gap = n / <span class="number">2</span>; gap >= <span class="number">1</span>; gap /= <span class="number">2</span>){</span><br><span class="line"> <span class="comment">//每个小组内使用插入排序</span></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = gap; i < n; i++){</span><br><span class="line"> <span class="comment">// 使用插入排序算法，将元素依次插入所在小组的已排序列表中</span></span><br><span class="line"> <span class="comment">// 待插入元素</span></span><br><span class="line"> <span class="keyword">int</span> itermToInsert = <span class="built_in">array</span>[i];</span><br><span class="line"> <span class="keyword">int</span> j = i - gap;</span><br><span class="line"> <span class="comment">//每个小组的第一个数字和末尾数字进行比较</span></span><br><span class="line"> <span class="keyword">while</span> (j >= <span class="number">0</span> && <span class="built_in">array</span>[j] >= itermToInsert){</span><br><span class="line"> <span class="comment">//小组内的第一个数字大于末尾数字，则进行交换</span></span><br><span class="line"> <span class="built_in">array</span>[j + gap] = <span class="built_in">array</span>[j];</span><br><span class="line"> <span class="comment">//j -= gap 为了跳出当前循环,进行下一组元素的交换</span></span><br><span class="line"> j -= gap;</span><br><span class="line"> }</span><br><span class="line"> <span class="built_in">array</span>[j + gap] = itermToInsert;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">Print</span><span class="params">(<span class="built_in">vector</span><<span class="keyword">int</span>>& <span class="built_in">array</span>)</span></span>{</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> & it : <span class="built_in">array</span>) {</span><br><span class="line"> <span class="built_in">cout</span> << it << <span class="string">" "</span>;</span><br><span class="line"> }<span class="built_in">cout</span> << <span class="built_in">endl</span>;</span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="built_in">vector</span><<span class="keyword">int</span>>arr;</span><br><span class="line"> arr.resize(<span class="number">100000</span>);</span><br><span class="line"> srand(time(<span class="literal">NULL</span>));</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < <span class="number">100000</span>; ++i) {</span><br><span class="line"> arr.push_back(rand()%<span class="number">100000</span>+<span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> shellSort(arr);</span><br><span class="line"> <span class="built_in">cout</span> << <span class="string">"The run time is:"</span> << (<span class="keyword">double</span>)clock() /CLOCKS_PER_SEC<< <span class="string">"s"</span> << <span class="built_in">endl</span>;</span><br><span class="line"> Print(arr);</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category>数据结构和算法</category>
</categories>
<tags>
<tag>排序</tag>
</tags>
</entry>
<entry>
<title>Win10快捷键</title>
<url>/posts/e5dc/</url>
<content><![CDATA[<p>1.创建虚拟桌面</p>
<p>Win+Alt+D / Win+Tab(可以通过鼠标操作虚拟桌面的创建、切换与删除)</p>
<p>Win+Ctrl+F4 关闭当前虚拟桌面</p>
<p>2.窗口最小化</p>
<p>Win+M 窗口最小化 Win+D 可在最小化全部窗口与恢复全部窗口状态 间自由切换</p>
<p>3.应用切换<br>Ctrl+Alt+Tab显示当前桌面运行的所有应用程序 Ctrl+Tab 切换任务</p>
<p>4.屏幕截图</p>
<p>Win + PrtSc/PrtSc /Win + Shift + S</p>
<p>5.任务管理器</p>
<p>Ctrl+Shift+Esc</p>
<p>6.文件资源管理器</p>
<p>Win+E </p>
<p>7.操作中心</p>
<p>win+A</p>
<p>8.打开设置</p>
<p>Win+I</p>
<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><div class="btn-center">
<a class="btn-beautify button--animated outline green larger" href="https://www.jb51.net/os/win10/226560.html" target="_blank" rel="noopener" title="Win10快捷键大全"><i class="far fa-hand-point-right fa-fw"></i> Win10快捷键大全 </a>
</div>
]]></content>
<categories>
<category>生产力</category>
</categories>
<tags>
<tag>Win10</tag>
</tags>
</entry>
<entry>
<title>位运算</title>
<url>/posts/ebce/</url>
<content><![CDATA[<h3 id="位运算符以及源码-反码-补码"><a href="#位运算符以及源码-反码-补码" class="headerlink" title="位运算符以及源码,反码,补码"></a>位运算符以及源码,反码,补码</h3><ul>
<li>二进制的最高位是符号位:0表示正数,1表示负数</li>
<li>正数三码合一,均相同</li>
<li><strong>负数</strong>的反码 = 符号位不变,其他位取反(0=>1,1=>0)</li>
<li><strong>负数</strong>的补码 = 反码 + 1</li>
<li>0的补码,原码都是0,+0的反码 = 0000 0000,-0的补码 = 1111 1111;</li>
<li><strong>计算机运算</strong>的时候都是以<strong>补码</strong>的方式来运行 原因:可以将正负数统一起来</li>
</ul>
<table>
<thead>
<tr>
<th>运算规则</th>
<th>描述</th>
</tr>
</thead>
<tbody><tr>
<td>&:按位与</td>
<td>相同为1,否则为0</td>
</tr>
<tr>
<td>|:按位或</td>
<td>有1为1,否则为0</td>
</tr>
<tr>
<td>^:按位异或</td>
<td>不同为1,否则为0</td>
</tr>
<tr>
<td>~:按位取反</td>
<td>1转换为0,0转换为1</td>
</tr>
</tbody></table>
<p>🌰举两个例子</p>
<p><strong>~2:对2取反</strong></p>
<ul>
<li>1.2是正数三码合一得到补码:</li>
</ul>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">#int占4个字节 1个字节等于8位</span><br><span class="line">补码: 00000000 00000000 00000000 00000010</span><br><span class="line">#进行取反</span><br><span class="line">补码: 11111111 11111111 11111111 11111101</span><br><span class="line">#将取反后得到的补码(11111111 11111111 11111111 11111101)转成源码</span><br><span class="line">#负数的补码 = 反码 + 1</span><br><span class="line">反码: 补码 - 1 = 11111111 11111111 11111111 11111100</span><br><span class="line">#负数的反码 = 符号位不变,其他位取反(0=>1,1=>0)</span><br><span class="line">源码: 10000000 00000000 00000000 00000011</span><br><span class="line">#对2取反的结果是-3</span><br><span class="line">~2 => -3</span><br></pre></td></tr></table></figure>
<blockquote>
<p>代码如下：</p>
</blockquote>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="keyword">int</span> a = ~<span class="number">2</span>;</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"a = %d"</span>,a);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/25/66509c6ebf73a738a3e86da02d1cab4f.png" alt="image-20200625172956190"></p>
<p><strong>2&-3:2对-3进行按位与运算</strong></p>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">#获取2的补码</span><br><span class="line">补码: 00000000 00000000 00000000 00000010</span><br><span class="line">#获取-3的源码</span><br><span class="line">源码: 10000000 00000000 00000000 00000011</span><br><span class="line">#负数的反码 = 符号位不变,其他位取反(0=>1,1=>0)</span><br><span class="line">反码: 11111111 11111111 11111111 11111100</span><br><span class="line">#获取-3的补码</span><br><span class="line">#负数的补码 = 反码 + 1</span><br><span class="line">补码: 11111111 11111111 11111111 11111101</span><br><span class="line"></span><br><span class="line">#将2和-3的补码进行运算</span><br><span class="line"> 2的补码: 00000000 00000000 00000000 00000010</span><br><span class="line">-3的补码: 11111111 11111111 11111111 11111101</span><br><span class="line">&: 相同为1,否则为0</span><br><span class="line">#运算结果 为0</span><br><span class="line">00000000 00000000 00000000 00000000</span><br></pre></td></tr></table></figure>
<blockquote>
<p>代码如下:</p>
</blockquote>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="keyword">int</span> b = <span class="number">2</span> & <span class="number">-3</span>;</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"b = %d"</span>,b);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/25/8739d86e6f646cbbc0daa0318c2a2dfb.png" alt="image-20200625175424053"></p>
<h3 id="移位运算符"><a href="#移位运算符" class="headerlink" title="移位运算符"></a>移位运算符</h3><p><strong>算术左移<<:</strong> <strong>符号位不变,低位补0</strong> </p>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">3 << 2，则是将数字3左移2位</span><br><span class="line">#首先把3转换为二进制数字</span><br><span class="line">00000000 00000000 00000000 00000011</span><br><span class="line">#把该数字高位(左侧)的两个零移出，其他的数字都朝左平移2位，最后在低位(右侧)的两个空位补零</span><br><span class="line">#转换为十进制是12</span><br><span class="line">0000 0000 0000 0000 0000 0000 0000 1100</span><br></pre></td></tr></table></figure>
<blockquote>
<p>代码如下:</p>
</blockquote>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="keyword">int</span> c = <span class="number">3</span> << <span class="number">2</span>;</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"c = %d"</span>,c);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/25/ae4bc9b8187b6a5973852f953ff48973.png" alt="image-20200625200949845"></p>
<p><strong>算术右移>></strong>: <strong>低位移出(舍弃)，高位的空位补符号位，即正数补零，负数补1。</strong></p>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">11 >> 2，则是将数字11右移2位</span><br><span class="line">#首先把11转换为二进制数字</span><br><span class="line">00000000 00000000 00000000 00001011</span><br><span class="line">#把低位的最后两个数字移出，因为该数字是正数，所以在高位补零</span><br><span class="line">#转换为十进制是2</span><br><span class="line">00000000 00000000 00000000 00000010</span><br><span class="line"></span><br><span class="line">-1 >> 2</span><br><span class="line">#获取-1的源码</span><br><span class="line">10000000 00000000 00000000 00000001</span><br><span class="line">#源码=>反码</span><br><span class="line">11111111 11111111 11111111 11111110</span><br><span class="line">#反码=>补码</span><br><span class="line">11111111 11111111 11111111 11111111</span><br><span class="line">#移动两位后 (补码)</span><br><span class="line">11111111 11111111 11111111 11111111</span><br><span class="line">#补码=>源码</span><br><span class="line">#转换为十进制是-1</span><br><span class="line">10000000 00000000 00000000 00000001</span><br></pre></td></tr></table></figure>
<blockquote>
<p>代码如下:</p>
</blockquote>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="keyword">int</span> d = <span class="number">11</span> >> <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">int</span> e = <span class="number">-1</span> >> <span class="number">2</span>;</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"d = %d e = %d"</span>,d,e);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/06/25/3499348d49718a15382fb71f28120f1d.png" alt="image-20200625201030080"></p>
<ul>
<li><h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2></li>
</ul>
<div class="btn-center">
<a class="btn-beautify button--animated outline green larger" href="https://www.bilibili.com/video/BV1qJ411z7Hf?p=57" target="_blank" rel="noopener" title="尚硅谷C语言入门"><i class="far fa-hand-point-right fa-fw"></i> 尚硅谷C语言入门 </a>
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</div>]]></content>
<categories>
<category>C</category>
</categories>
<tags>
<tag>计算机基础知识</tag>
<tag>位运算</tag>
</tags>
</entry>
<entry>
<title>函数</title>
<url>/posts/5409/</url>
<content><![CDATA[<h2 id="函数的初步了解"><a href="#函数的初步了解" class="headerlink" title="函数的初步了解"></a>函数的初步了解</h2><ul>
<li><p>为完成某一功能的<strong>程序指令（语句）的集合</strong>称为<code>函数</code></p>
</li>
<li><p>在C语言中，函数分为：<code>自定义函数</code>、<code>系统函数</code></p>
<ul>
<li>C语言在线手册 <a href="http://www.dba.cn/book/c/CJiChuJiaoCheng/CJiBenYuFa.html" target="_blank" rel="noopener">http://www.dba.cn/book/c/CJiChuJiaoCheng/CJiBenYuFa.html</a></li>
</ul>
</li>
<li><p>函数还有其它名称，方法等</p>
</li>
</ul>
<p><strong>函数的基本语法</strong></p>
<figure class="highlight plain"><table><tr><td class="code"><pre><span class="line">返回类型 函数名 (形参){</span><br><span class="line"> 执行语句;</span><br><span class="line"> return 返回值;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li><code>形参</code>表示<strong>函数的输入</strong></li>
<li>函数中的<code>执行语句</code> <strong>实现某一功能代码块</strong></li>
<li>函数可以有返回值，也可以没有，如果没有返回值，返回类型声明为void</li>
</ul>
<h2 id="头文件"><a href="#头文件" class="headerlink" title="头文件"></a>头文件</h2><p><strong>需求</strong>：实际开发中<strong>需要在不同文件中调用其他文件中的函数</strong></p>
<p><strong>基本概念</strong></p>
<ul>
<li><p><code>头文件</code>是<strong>扩展名为h</strong>的文件，包含了<code>C函数声明</code>和<code>宏定义</code>，<strong>被多个源文件中引用共享</strong>。</p>
</li>
<li><p>头文件的类型的开发者<strong>自己编写的头文件</strong>和<strong>C标准库自带的头文件</strong></p>
</li>
<li><p>程序中要使用头文件，需要使用<code>C预处理指令#include</code>来引用。<code>stdio. h</code>头文件，是C标准库自带的头文件</p>
</li>
<li><p>文件包含命令(<code>#include</code>)，用来引入对应的头文件（h文件）。#include的<strong>处理过程</strong>是将<strong>头文件的内容插入到该命令所在的位置</strong>，使得<code>头文件</code>和<code>当前源文件</code><strong>连接成一个源文件</strong>，与复制粘贴的效果相同。直接在源文件中复制头文件的内容，容易出错，特别在程序是由多个源文件组成的时候。</p>
</li>
<li><p>所有的<code>常量</code>、<code>宏</code>、<code>系统全局变量</code>和<code>函数原型</code>写在<code>头文件</code>中，需要的时候随时再引用头文件</p>
</li>
</ul>
<p> <strong>工作原理图</strong></p>
<p><img src= "/img/loading.gif" data-src="https://cdn.jsdelivr.net/gh/L0serH4/mycdn@master/2020/07/08/400f7ef8cad9d26182ce82e0a80624f1.png" alt="image-20200708163738567"></p>
<ul>
<li>func.h头文件和func.c源文件<strong>名称一般相同</strong>为了使用</li>
</ul>
<p><strong>头文件的注意事项和细节说明</strong></p>
<ul>
<li><p><strong>引用头文件相当于复制头文件的内容，注意路径问题</strong></p>
</li>
<li><p>C语言中 include<>与 include””的区别include<> ：</p>
<ul>
<li><code>include<></code>: 引用的是编译器的类库路径里面的头文件，用于<strong>引用系统头文件</strong></li>
<li><code>include””</code>：引用的是程序<strong>目录的相对路径中的头文件</strong>，</li>
<li>如果在<strong>程序目录</strong>没有找到引用的头文件则到<strong>编译器的类库路径</strong>的目录下找该头文件，</li>
<li>引用<strong>系统头文件</strong>，两种形式·都可以，include<>效率</li>
<li>引用<strong>用户头文件</strong>，只能使用 include””</li>
</ul>
</li>
<li><p>一个#include命令只能包含一个头文件，多个头文件需要多个# include命令</p>
</li>
<li><p>同一个头文件如果被多次引入，<strong>多次引入的效果和一次引入的效果相同</strong>，因为<strong>头文件在代码层面有防止重复引入的机制</strong></p>
</li>
<li><p>在一个被包含的文件.c中又可以包含另一个文件头文件.h</p>
</li>
<li><p>不管是<code>标准头文件</code>，还是<code>自定义头文件</code>，都<strong>只能包含变量和函数的声明</strong>，<strong>不能包含定义</strong>，否则在<strong>多次引入时会引起重复定义错误</strong></p>
</li>
</ul>
<h2 id="函数的调用机制"><a href="#函数的调用机制" class="headerlink" title="函数的调用机制"></a>函数的调用机制</h2><p>函数调用的规则适用于: <code>java</code>,<code>c++</code>，<code>php</code>等）</p>
<ul>
<li>当调用(执行)一个函数时，就会开辟一个独立的空间(栈)</li>
<li>每个栈空间是相互独立</li>
<li>当函数执行完毕后，会返回到调用函数位置，继续执行</li>
<li>函数有返回值，将返回值赋给接收的变量 当一个函数返回后，该函数对应的栈空间也就销毀</li>
</ul>
<h2 id="函数的递归调用"><a href="#函数的递归调用" class="headerlink" title="函数的递归调用"></a>函数的递归调用</h2><p><strong>一个函数在函数体内又调用了函数本身，称为递归调用</strong></p>
<ul>
<li><p>执行一个函数时，就创建一个新的受保护的独立空间（新函数栈）</p>
</li>
<li><p>函数的局部变量是独立的，不会相互影响</p>
</li>
<li><p>递归必须向退出递归的条件逼近，否则就是无限递归,造成栈溢出(StackOverFlow)</p>
</li>
<li><p>当一个函数执行完毕，或者遇到 return，就会返回，将结果返回给调用处</p>
</li>
</ul>
<p>🌰<strong>举例</strong></p>
<p>求出斐波那契数1,1,2,3,5,8,13.求整数n对应的斐波那契数</p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">fbn</span><span class="params">(<span class="keyword">int</span> n)</span></span>{</span><br><span class="line"> <span class="keyword">if</span>(n=<span class="number">1</span> || n==<span class="number">2</span>){</span><br><span class="line"> <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">else</span>{</span><br><span class="line"> <span class="keyword">return</span> fbn(n<span class="number">-1</span>)+ fbn(n<span class="number">-2</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="keyword">int</span> res = fbn(<span class="number">10</span>);</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"res = %d"</span>,res);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>有一堆桃子，猴子第一天吃了其中的一半，并再多吃了一个,以后每天猴子都吃其中的一半，然后再多吃一个。当到第十天时，想再吃时（还没吃），发现只有1个桃子了。求最初多少桃子？</p>
<figure class="highlight c"><table><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">peach</span><span class="params">(<span class="keyword">int</span> day)</span></span>{</span><br><span class="line"> <span class="keyword">if</span>(day=<span class="number">10</span>){</span><br><span class="line"> <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span>{</span><br><span class="line"> <span class="keyword">return</span> (peach(day+<span class="number">1</span>)+<span class="number">1</span>)*<span class="number">2</span>;</span><br><span class="line"> } </span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">main</span><span class="params">()</span></span>{</span><br><span class="line"> <span class="comment">//分析过程</span></span><br><span class="line"> <span class="comment">//1.day=10有1个桃子</span></span><br><span class="line"> <span class="comment">//2.day=9有(day10+1)*2=（1+1）*2=4</span></span><br><span class="line"> <span class="comment">//3.day=8 (day9+1)*2=(4+1)*2=10</span></span><br><span class="line"> <span class="keyword">int</span> peachUm = peach(<span class="number">1</span>);</span><br><span class="line"> <span class="built_in">printf</span>(<span class="string">"第一天有%d个桃子"</span>,peachUm);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>