209 lines
14 KiB
HTML
209 lines
14 KiB
HTML
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<title>qsort, qsort_s</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_algorithm_qsort skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading">qsort, qsort_s</h1>
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-algorithm.html">algorithm</a></span></div>
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<div>定义于头文件 <code><stdlib.h></code></div>
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<div><span class="mw-geshi c source-c"><span class="kw4">void</span> qsort<span class="br0">(</span> <span class="kw4">void</span> <span class="sy2">*</span>ptr, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> count, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> size,<br />
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<span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span>comp<span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">void</span> <span class="sy2">*</span>, <span class="kw4">const</span> <span class="kw4">void</span> <span class="sy2">*</span><span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td class="t-dcl-nopad"></td>
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<div><span class="mw-geshi c source-c">errno_t qsort_s<span class="br0">(</span> <span class="kw4">void</span> <span class="sy2">*</span>ptr, rsize_t count, rsize_t size,<br /></span>
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<p> <span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span>comp<span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">void</span> <span class="sy2">*</span>, <span class="kw4">const</span> <span class="kw4">void</span> <span class="sy2">*</span>, <span class="kw4">void</span> <span class="sy2">*</span><span class="br0">)</span>,<br /></p>
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<span class="kw4">void</span> <span class="sy2">*</span>context <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 对 <code>ptr</code> 所指向的数组以升序排序。数组包含 <code>count</code> 个长度为 <code>size</code> 字节的元素。用 <code>comp</code> 所指向的函数比较对象。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，除了传递给 <code>comp</code> 附加环境参数 <code>context</code> ，还会在运行时检测下列错误，并调用当前安装的<a href="c-error-set_constraint_handler_s.html">制约处理</a>函数：
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<dl>
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<dd>
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<li><code>count</code> 或 <code>size</code> 大于 <span class="t-lc">RSIZE_MAX</span></li>
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<li><code>key</code> 、 <code>ptr</code> 或 <code>comp</code> 是空指针（除非 <code>count</code> 为零）</li>
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</ul>
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</dd>
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<dd></dd>
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<dd>同所有边界检查函数， <code>qsort_s</code> 仅若实现定义了 <span class="t-c"><span class="mw-geshi c source-c">__STDC_LIB_EXT1__</span></span> ，且用户在包含 <code>stdlib.h</code> 前定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_WANT_LIB_EXT1__</span></span> 为整数常量 <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">1</span></span></span> 才保证可用。</dd>
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</dl>
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<p>若 <code>comp</code> 指示两元素相等，则它们排序后的结果是未指定的。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<td>ptr</td>
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<td>-</td>
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<td>指向待排序的数组的指针</td>
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</tr>
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<tr class="t-par">
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<td>count</td>
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<td>-</td>
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<td>数组的元素数目</td>
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</tr>
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<tr class="t-par">
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<td>size</td>
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<td>-</td>
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<td>数组每个元素的字节大小</td>
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</tr>
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<tr class="t-par">
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<td>comp</td>
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<td>-</td>
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<td>比较函数。若首个参数<i>小于</i>第二个，则返回负整数值，若首个参数<i>大于</i>第二个，则返回正整数值，若两参数等价，则返回零。<br />
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<p>比较函数的签名应等价于如下形式：</p>
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<p><span class="t-cc"><span class="mw-geshi c source-c"> <span class="kw4">int</span> cmp<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">void</span> <span class="sy2">*</span>a, <span class="kw4">const</span> <span class="kw4">void</span> <span class="sy2">*</span>b<span class="br0">)</span><span class="sy4">;</span></span></span></p>
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<p>该函数必须不修改传递给它的对象，而且在调用比较相同对象时必须返回一致的结果，无关乎它们在数组中的位置。</p>
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<p>​</p>
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</td>
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</tr>
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<tr class="t-par">
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<td>context</td>
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<td>-</td>
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<td>附加信息（例如，对照序列），作为第三个参数传递给 <code>comp</code></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<div class="t-li1"><span class="t-li">1)</span> （无）</div>
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<div class="t-li1"><span class="t-li">2)</span> 成功时为零，若检测到运行时制约违规，则为非零</div>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>与名称无关，C 和 POSIX 标准都未要求此函数用<a href="https://en.wikipedia.org/wiki/Quicksort" class="extiw" title="enwiki:Quicksort">快速排序</a>实现，也未保证任何复杂度或稳定性。</p>
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<p>与其他边界检查函数不同， <code>qsort_s</code> 不将零大小数组视作运行时强制违规，而是不修改数组并成功返回（另一个接受零大小数组的函数是 <span class="t-lc">bsearch_s</span> ）。</p>
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<p>在 <code>qsort_s</code> 之前，<code>qsort</code> 的用户通常用全局变量来将附加语境传递给比较函数。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <stdlib.h></span>
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<span class="co2">#include <limits.h></span>
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<span class="kw4">int</span> compare_ints<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">void</span><span class="sy2">*</span> a, <span class="kw4">const</span> <span class="kw4">void</span><span class="sy2">*</span> b<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">int</span> arg1 <span class="sy1">=</span> <span class="sy2">*</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span><span class="sy2">*</span><span class="br0">)</span>a<span class="sy4">;</span>
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<span class="kw4">int</span> arg2 <span class="sy1">=</span> <span class="sy2">*</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span><span class="sy2">*</span><span class="br0">)</span>b<span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>arg1 <span class="sy1"><</span> arg2<span class="br0">)</span> <span class="kw1">return</span> <span class="sy2">-</span><span class="nu0">1</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>arg1 <span class="sy1">></span> arg2<span class="br0">)</span> <span class="kw1">return</span> <span class="nu0">1</span><span class="sy4">;</span>
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<span class="kw1">return</span> <span class="nu0">0</span><span class="sy4">;</span>
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<span class="co1">// return (arg1 > arg2) - (arg1 < arg2); // 可行的简写</span>
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<span class="co1">// return arg1 - arg2; // 错误的简写（若给出 INT_MIN 则会失败）</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">int</span> ints<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span> <span class="sy2">-</span><span class="nu0">2</span>, <span class="nu0">99</span>, <span class="nu0">0</span>, <span class="sy2">-</span><span class="nu0">743</span>, <span class="nu0">2</span>, <a href="c-types-limits.html"><span class="kw359">INT_MIN</span></a>, <span class="nu0">4</span> <span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">int</span> size <span class="sy1">=</span> <span class="kw4">sizeof</span> ints <span class="sy2">/</span> <span class="kw4">sizeof</span> <span class="sy2">*</span>ints<span class="sy4">;</span>
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qsort<span class="br0">(</span>ints, size, <span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span>, compare_ints<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> i <span class="sy1"><</span> size<span class="sy4">;</span> i<span class="sy2">++</span><span class="br0">)</span> <span class="br0">{</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%d "</span>, ints<span class="br0">[</span>i<span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">-2147483648 -743 -2 0 2 4 99</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.22.5.2 The qsort function (p: 355-356)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>K.3.6.3.2 The qsort_s function (p: 609)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.20.5.2 The qsort function (p: 319)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>4.10.5.2 The qsort function</li>
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</ul>
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</dd>
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</dl>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="c-algorithm-bsearch.html"><span class="t-lines"><span>bsearch</span><span>bsearch_s</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>在未指定类型的数组中搜索一个元素<br />
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<span class="t-mark">(函数)</span></td>
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