302 lines
26 KiB
HTML
302 lines
26 KiB
HTML
<!DOCTYPE html>
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<title>std::is_permutation</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_is_permutation skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>is_permutation</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-algorithm.html">algorithm</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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<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 rowspan="142">(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br /></p>
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ForwardIt2 first2 <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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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> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br /></p>
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ForwardIt2 first2 <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td></td>
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<td rowspan="142">(2)</td>
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<td></td>
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<tr class="t-dcl t-since-cxx11 t-until-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br /></p>
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ForwardIt2 first2, BinaryPredicate p <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</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> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br /></p>
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ForwardIt2 first2, BinaryPredicate p <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<tr class="t-dcl-rev-aux">
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<td></td>
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<td rowspan="142">(3)</td>
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<td></td>
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<tr class="t-dcl t-since-cxx14 t-until-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br /></p>
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ForwardIt2 first2, ForwardIt2 last2 <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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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> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br /></p>
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ForwardIt2 first2, ForwardIt2 last2 <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td></td>
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<td rowspan="142">(4)</td>
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<td></td>
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<tr class="t-dcl t-since-cxx14 t-until-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br />
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ForwardIt2 first2, ForwardIt2 last2,<br /></p>
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BinaryPredicate p <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">bool</span> is_permutation<span class="br0">(</span> ForwardIt1 first1, ForwardIt1 last1,<br />
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ForwardIt2 first2, ForwardIt2 last2,<br /></p>
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BinaryPredicate p <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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<p>若存在范围 <code>[first1, last1)</code> 中元素的排列，使得该范围等于 <code>[first2,last2)</code> ，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，若不给出，则其中 <code>last2</code> 代表 <span class="t-c"><span class="mw-geshi cpp source-cpp">first2 <span class="sy2">+</span> <span class="br0">(</span>last1 <span class="sy2">-</span> first1<span class="br0">)</span></span></span> 。</p>
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<div class="t-li1"><span class="t-li">1,3)</span> 用 <code>operator==</code> 比较元素。若它不是<a href="https://en.wikipedia.org/wiki/equivalence_relation" class="extiw" title="enwiki:equivalence relation">等价关系</a>则行为未定义。</div>
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<div class="t-li1"><span class="t-li">2,4)</span> 用给定的二元谓词 <code>p</code> 比较元素。若它不是等价关系则行为未定义。</div>
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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>first1, last1</td>
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<td>-</td>
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<td>要比较的元素范围</td>
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</tr>
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<tr class="t-par">
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<td>first2, last2</td>
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<td>-</td>
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<td>要比较的第二范围</td>
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</tr>
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<tr class="t-par">
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<td>p</td>
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<td>-</td>
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<td>若应把元素当做相等则返回 ​<span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 的二元谓词。<br />
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<p>谓词函数的签名应等价于如下：</p>
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<p><span class="t-cc"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span> pred<span class="br0">(</span><span class="kw4">const</span> Type <span class="sy3">&</span>a, <span class="kw4">const</span> Type <span class="sy3">&</span>b<span class="br0">)</span><span class="sy4">;</span></span></span></p>
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<p><code>Type</code> 应是 <code>ForwardIt1</code> 和 <code>ForwardIt2</code> 两者的值类型。签名不必有 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <span class="sy3">&</span></span></span> ，但函数必须不修改传递给它的对象。 ​</p>
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</td>
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<tr class="t-par-hitem">
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<td colspan="3">类型要求</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>ForwardIt1, ForwardIt2</code> 必须满足<a href="cpp-named_req-ForwardIterator.html"><span style="font-style:italic">老式向前迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyForwardIterator)</span></a> 的要求。</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>ForwardIt1</code> 与 <code>ForwardIt2</code> 必须拥有相同的值类型。</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>若范围 <code>[first1, last1)</code> 是 <code>[first2, last2)</code> 的排列则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 。</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>至多应用 <span class="mjax" style="display:none">\(\scriptsize \mathcal{O}(N^2)\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">O(N<sup>2</sup>)</span> 次谓词，或若序列已经相等，则准确应用 <span class="mjax" style="display:none">\(\scriptsize N\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">N</span> 次，其中 <span class="mjax" style="display:none">\(\scriptsize N\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">N</span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-distance.html"><span class="kw673">std::<span class="me2">distance</span></span></a><span class="br0">(</span>first1, last1<span class="br0">)</span></span></span> 。</p>
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<p>然而，若 <code>ForwardIt1</code> 和 <code>ForwardIt2</code> 满足<a href="cpp-named_req-RandomAccessIterator.html"><span style="font-style:italic">老式随机访问迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyRandomAccessIterator)</span></a> 的要求且 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-distance.html"><span class="kw673">std::<span class="me2">distance</span></span></a><span class="br0">(</span>first1, last1<span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> <a href="cpp-iterator-distance.html"><span class="kw673">std::<span class="me2">distance</span></span></a><span class="br0">(</span>first2, last2<span class="br0">)</span></span></span> ，则不应用谓词。 <i>排列</i>关系是<a href="https://en.wikipedia.org/wiki/equivalence_relation" class="extiw" title="enwiki:equivalence relation">等价关系</a>。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p><strong class="selflink"><tt>std::is_permutation</tt></strong> 能用于按照其名称地<i>测试</i>重排算法（例如排序、打乱、划分）的正确性。若 <code>x</code> 为原范围而 <code>y</code> 是<i>重排后</i>范围则 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">is_permutation</span><span class="br0">(</span>x, y<span class="br0">)</span> <span class="sy1">==</span> <span class="kw2">true</span></span></span> 表示 <code>y</code> 由可能位于其他位置的<i>“相同”</i>元素组成。</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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<tr>
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<td>
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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">template</span><span class="sy1"><</span><span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2<span class="sy1">></span>
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<span class="kw4">bool</span> is_permutation<span class="br0">(</span>ForwardIt1 first, ForwardIt1 last,
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ForwardIt2 d_first<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="co1">// 跳过公共前缀</span>
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<a href="cpp-utility-tuple-tie.html"><span class="kw1113">std::<span class="me2">tie</span></span></a><span class="br0">(</span>first, d_first<span class="br0">)</span> <span class="sy1">=</span> <a href="cpp-algorithm-mismatch.html"><span class="kw1572">std::<span class="me2">mismatch</span></span></a><span class="br0">(</span>first, last, d_first<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 在 rest 上迭代，计数 [d_first, d_last) 中出现多少次</span>
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<span class="co1">// 每个来自 [first, last) 的元素</span>
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<span class="kw1">if</span> <span class="br0">(</span>first <span class="sy3">!</span><span class="sy1">=</span> last<span class="br0">)</span> <span class="br0">{</span>
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ForwardIt2 d_last <span class="sy1">=</span> d_first<span class="sy4">;</span>
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<a href="cpp-iterator-advance.html"><span class="kw672">std::<span class="me2">advance</span></span></a><span class="br0">(</span>d_last, <a href="cpp-iterator-distance.html"><span class="kw673">std::<span class="me2">distance</span></span></a><span class="br0">(</span>first, last<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>ForwardIt1 i <span class="sy1">=</span> first<span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> last<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">if</span> <span class="br0">(</span>i <span class="sy3">!</span><span class="sy1">=</span> <a href="cpp-algorithm-find_if_not.html"><span class="kw1574">std::<span class="me2">find</span></span></a><span class="br0">(</span>first, i, <span class="sy2">*</span>i<span class="br0">)</span><span class="br0">)</span> <span class="kw1">continue</span><span class="sy4">;</span> <span class="co1">// 已经遇到此 *i</span>
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<span class="kw4">auto</span> m <span class="sy1">=</span> <a href="cpp-algorithm-count_if.html"><span class="kw1570">std::<span class="me2">count</span></span></a><span class="br0">(</span>d_first, d_last, <span class="sy2">*</span>i<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>m<span class="sy1">==</span><span class="nu0">0</span> <span class="sy3">||</span> <a href="cpp-algorithm-count_if.html"><span class="kw1570">std::<span class="me2">count</span></span></a><span class="br0">(</span>i, last, <span class="sy2">*</span>i<span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> m<span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span>
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<span class="br0">}</span>
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<span class="kw1">return</span> <span class="kw2">true</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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</td>
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</tr>
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</table>
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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 <iostream></span>
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<span class="co2">#include <algorithm></span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">typename</span> Os, <span class="kw1">typename</span> V<span class="sy1">></span>
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Os<span class="sy3">&</span> operator<span class="sy1"><<</span> <span class="br0">(</span>Os<span class="sy3">&</span> os, V <span class="kw4">const</span><span class="sy3">&</span> v<span class="br0">)</span> <span class="br0">{</span>
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os <span class="sy1"><<</span> <span class="st0">"{ "</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">auto</span> <span class="kw4">const</span><span class="sy3">&</span> e <span class="sy4">:</span> v<span class="br0">)</span> os <span class="sy1"><<</span> e <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
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<span class="kw1">return</span> os <span class="sy1"><<</span> <span class="st0">"}"</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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<span class="kw4">static</span> <span class="kw4">constexpr</span> <span class="kw4">auto</span> v1 <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">1</span>,<span class="nu0">2</span>,<span class="nu0">3</span>,<span class="nu0">4</span>,<span class="nu0">5</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">static</span> <span class="kw4">constexpr</span> <span class="kw4">auto</span> v2 <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">3</span>,<span class="nu0">5</span>,<span class="nu0">4</span>,<span class="nu0">1</span>,<span class="nu0">2</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">static</span> <span class="kw4">constexpr</span> <span class="kw4">auto</span> v3 <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">3</span>,<span class="nu0">5</span>,<span class="nu0">4</span>,<span class="nu0">1</span>,<span class="nu0">1</span><span class="br0">}</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> v2 <span class="sy1"><<</span> <span class="st0">" is a permutation of "</span> <span class="sy1"><<</span> v1 <span class="sy1"><<</span> <span class="st0">": "</span> <span class="sy1"><<</span> <a href="cpp-io-manip-boolalpha.html"><span class="kw1763">std::<span class="me2">boolalpha</span></span></a>
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<span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">is_permutation</span><span class="br0">(</span>v1.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, v1.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, v2.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> v3 <span class="sy1"><<</span> <span class="st0">" is a permutation of "</span> <span class="sy1"><<</span> v1 <span class="sy1"><<</span> <span class="st0">": "</span> <span class="sy1"><<</span> <a href="cpp-io-manip-boolalpha.html"><span class="kw1763">std::<span class="me2">boolalpha</span></span></a>
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<span class="sy1"><<</span> std<span class="sy4">::</span><span class="me2">is_permutation</span><span class="br0">(</span>v1.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, v1.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, v3.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <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></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">{ 3 5 4 1 2 } is a permutation of { 1 2 3 4 5 }: true
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{ 3 5 4 1 1 } is a permutation of { 1 2 3 4 5 }: false</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-next_permutation.html"><span class="t-lines"><span>next_permutation</span></span></a></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顺序的下一个较大的排列<br />
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<span class="t-mark">(函数模板)</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-prev_permutation.html"><span class="t-lines"><span>prev_permutation</span></span></a></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顺序的下一个较小的排列<br />
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<span class="t-mark">(函数模板)</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-concepts-equivalence_relation.html"><span class="t-lines"><span>equivalence_relation</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>指定 <a href="cpp-concepts-relation.html"><code>relation</code></a> 施加等价关系<br />
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<span class="t-mark">(概念)</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-is_permutation.html"><span class="t-lines"><span>ranges::is_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>确定一个序列是否为另一序列的重排<br />
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<span class="t-mark">(niebloid)</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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