208 lines
17 KiB
HTML
208 lines
17 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>std::ranges::shuffle</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_ranges_shuffle skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ranges::</span>shuffle</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-algorithm.html">algorithm</a>‎ | <a href="cpp-algorithm-ranges.html">ranges</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-algorithm.html"><algorithm></a></code></div>
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<td></td>
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<td>
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<div>调用签名</div>
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</td>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> std<span class="sy4">::</span><span class="me2">random_access_iterator</span> I, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I<span class="sy1">></span> S, <span class="kw1">class</span> Gen <span class="sy1">></span><br /></span>
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<p>requires std<span class="sy4">::</span><span class="me2">permutable</span><span class="sy1"><</span>I<span class="sy1">></span> <span class="sy3">&&</span><br />
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std<span class="sy4">::</span><span class="me2">uniform_random_bit_generator</span><span class="sy1"><</span><a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>Gen<span class="sy1">>></span><br /></p>
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I shuffle<span class="br0">(</span> I first, S last, Gen<span class="sy3">&&</span> gen <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<tr class="t-dcl t-since-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> ranges<span class="sy4">::</span><span class="me2">random_access_range</span> R, <span class="kw1">class</span> Gen <span class="sy1">></span><br /></span>
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<p>requires std<span class="sy4">::</span><span class="me2">permutable</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">>></span> <span class="sy3">&&</span><br />
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std<span class="sy4">::</span><span class="me2">uniform_random_bit_generator</span><span class="sy1"><</span><a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>Gen<span class="sy1">>></span><br /></p>
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ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span> shuffle<span class="br0">(</span> R<span class="sy3">&&</span> r, Gen<span class="sy3">&&</span> gen <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-cxx20">(C++20 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 重排给定范围 <code>[first, last)</code> 中的元素以使得那些元素的每个可能排列拥有相等的出现概率。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，但以 <code>r</code> 为范围，如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 为 <code>first</code> 并以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 为 <code>last</code> 。</div>
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<p>此页面上描述的仿函数实体是 <i>niebloid</i> ，即：</p>
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<ul>
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<li>调用它们中的任何一者时不可指定显式模板实参。</li>
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<li>它们无一对<a href="cpp-language-adl.html">实参依赖查找</a>可见。</li>
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<li>在<a href="cpp-language-unqualified_lookup.html">通常无限定查找</a>寻找函数调用运算符左侧的名称找到它们之一时，它禁止<a href="cpp-language-adl.html">实参依赖查找</a>。</li>
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</ul>
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<p>实际上，它们能以函数对象，或以某些特殊编译器扩展实现。</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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<tr class="t-par">
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<td>first, last</td>
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<td>-</td>
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<td>要随机打乱的范围</td>
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<tr class="t-par">
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<td>r</td>
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<td>-</td>
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<td>要随机打乱的范围</td>
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<tr class="t-par">
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<td>gen</td>
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<td>-</td>
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<td>随机数生成器</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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<p>等于 <code>last</code> 的迭代器。</p>
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<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
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<p>准确交换 <code>(last - first) - 1</code> 次。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<table class="eq-fun-cpp-table">
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="kw1">struct</span> shuffle_fn <span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">random_access_iterator</span> I, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I<span class="sy1">></span> S, <span class="kw1">class</span> Gen<span class="sy1">></span>
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requires std<span class="sy4">::</span><span class="me2">permutable</span><span class="sy1"><</span>I<span class="sy1">></span> <span class="sy3">&&</span>
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std<span class="sy4">::</span><span class="me2">uniform_random_bit_generator</span><span class="sy1"><</span><a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>Gen<span class="sy1">>></span>
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I operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span> I first, S last, Gen<span class="sy3">&&</span> gen <span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
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<span class="kw1">using</span> diff_t <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">iter_difference_t</span><span class="sy1"><</span>I<span class="sy1">></span><span class="sy4">;</span>
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<span class="kw1">using</span> distr_t <span class="sy1">=</span> <a href="cpp-numeric-random-uniform_int_distribution.html"><span class="kw1502">std::<span class="me2">uniform_int_distribution</span></span></a><span class="sy1"><</span>diff_t<span class="sy1">></span><span class="sy4">;</span>
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<span class="kw1">using</span> param_t <span class="sy1">=</span> <span class="kw1">typename</span> distr_t<span class="sy4">::</span><span class="me2">param_type</span><span class="sy4">;</span>
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distr_t D<span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> n<span class="br0">{</span> last <span class="sy2">-</span> first <span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span>diff_t i<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> n<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
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ranges<span class="sy4">::</span><span class="me2">iter_swap</span><span class="br0">(</span>first <span class="sy2">+</span> i, first <span class="sy2">+</span> D<span class="br0">(</span>gen, param_t<span class="br0">(</span><span class="nu0">0</span>, i<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">return</span> ranges<span class="sy4">::</span><span class="me2">next</span><span class="br0">(</span>first, last<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">random_access_range</span> R, <span class="kw1">class</span> Gen<span class="sy1">></span>
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requires std<span class="sy4">::</span><span class="me2">permutable</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">>></span> <span class="sy3">&&</span>
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std<span class="sy4">::</span><span class="me2">uniform_random_bit_generator</span><span class="sy1"><</span><a href="cpp-types-remove_reference.html"><span class="kw607">std::<span class="me2">remove_reference_t</span></span></a><span class="sy1"><</span>Gen<span class="sy1">>></span>
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ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span> R<span class="sy3">&&</span> r, Gen<span class="sy3">&&</span> gen <span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span><span class="br0">(</span>ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r<span class="br0">)</span>, ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>gen<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">inline</span> <span class="kw4">constexpr</span> shuffle_fn shuffle<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></pre></div>
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</div>
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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="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <algorithm></span>
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<span class="co2">#include <array></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <random></span>
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<span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">auto</span><span class="sy3">&</span> a<span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">const</span> <span class="kw4">auto</span> e <span class="sy4">:</span> a<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> e <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span> <span class="br0">}</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>"</span><span class="sy4">;</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="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a> a<span class="br0">{</span><span class="st0">'A'</span>, <span class="st0">'B'</span>, <span class="st0">'C'</span>, <span class="st0">'D'</span>, <span class="st0">'E'</span>, <span class="st0">'F'</span><span class="br0">}</span><span class="sy4">;</span>
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print<span class="br0">(</span>a<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-numeric-random-random_device.html"><span class="kw1486">std::<span class="me2">random_device</span></span></a> rd<span class="sy4">;</span>
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<a href="cpp-numeric-random-mersenne_twister_engine.html"><span class="kw1489">std::<span class="me2">mt19937</span></span></a> gen<span class="br0">{</span>rd<span class="br0">(</span><span class="br0">)</span><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="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">3</span><span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
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std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">shuffle</span><span class="br0">(</span>a, gen<span class="br0">)</span><span class="sy4">;</span>
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print<span class="br0">(</span>a<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>可能的输出：</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">A B C D E F
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F E A C D B
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E C B F A D
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B A E C F D</pre></div>
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</div>
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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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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-next_permutation.html"><span class="t-lines"><span>ranges::next_permutation</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>产生某个元素范围的按字典序下一个较大的排列<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-prev_permutation.html"><span class="t-lines"><span>ranges::prev_permutation</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>产生某个元素范围的按字典序下一个较小的排列<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-random_shuffle.html"><span class="t-lines"><span>random_shuffle</span><span>shuffle</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>随机重排范围中的元素<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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