194 lines
15 KiB
HTML
194 lines
15 KiB
HTML
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<title>std::rotate_copy</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_rotate_copy 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>rotate_copy</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>定义于头文件 <code><a href="cpp-header-algorithm.html"><algorithm></a></code></div>
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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> ForwardIt, <span class="kw1">class</span> OutputIt <span class="sy1">></span><br /></span>
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<p>OutputIt rotate_copy<span class="br0">(</span> ForwardIt first, ForwardIt n_first,<br /></p>
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ForwardIt last, OutputIt d_first <span class="br0">)</span><span class="sy4">;</span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></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> ForwardIt, <span class="kw1">class</span> OutputIt <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> OutputIt rotate_copy<span class="br0">(</span> ForwardIt first, ForwardIt n_first,<br /></p>
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ForwardIt last, OutputIt d_first <span class="br0">)</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></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> ExecutionPolicy, <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2 <span class="sy1">></span><br /></span>
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<p>ForwardIt2 rotate_copy<span class="br0">(</span> ExecutionPolicy<span class="sy3">&&</span> policy,<br />
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ForwardIt1 first, ForwardIt1 n_first,<br /></p>
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ForwardIt1 last, ForwardIt2 d_first <span class="br0">)</span><span class="sy4">;</span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 从范围 <code>[first, last)</code> 复制元素到始于 <code>d_first</code> 的另一范围，使得 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>n_first</span></span> 成为新范围的首元素，而 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span><span class="br0">(</span>n_first <span class="sy2">-</span> <span class="nu0">1</span><span class="br0">)</span></span></span> 成为末元素。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，但按照 <code>policy</code> 执行。此重载仅若 <span class="t-rev-inl t-until-cxx20"><span><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-algorithm-is_execution_policy.html"><span class="kw1564">std::<span class="me2">is_execution_policy_v</span></span></a><span class="sy1"><</span><a href="cpp-types-decay.html"><span class="kw629">std::<span class="me2">decay_t</span></span></a><span class="sy1"><</span>ExecutionPolicy<span class="sy1">>></span></span></span></span> <span><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></span></span><span class="t-rev-inl t-since-cxx20"><span><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-algorithm-is_execution_policy.html"><span class="kw1564">std::<span class="me2">is_execution_policy_v</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>ExecutionPolicy<span class="sy1">>></span></span></span></span> <span><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></span> 为 true 才参与重载决议。</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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<td>first, last</td>
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<td>-</td>
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<td>要复制的元素范围</td>
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<td>n_first</td>
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<td>-</td>
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<td>指向 <code>[first, last)</code> 中应出现在新范围起始的元素的迭代器</td>
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<td>d_first</td>
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<td>-</td>
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<td>目标范围的起始</td>
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<tr class="t-par">
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<td>policy</td>
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<td>-</td>
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<td>所用的执行策略。细节见<a href="cpp-algorithm-execution_policy_tag_t.html">执行策略</a>。</td>
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<td colspan="3">类型要求</td>
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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>ForwardIt, 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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<td colspan="3">-
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<div class="spacer"></div>
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<code>OutputIt</code> 必须满足<a href="cpp-named_req-OutputIterator.html"><span style="font-style:italic">老式输出迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyOutputIterator)</span></a> 的要求。</td>
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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>指向最后被复制元素后一元素的输出迭代器。</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>与 <code>first</code> 和 <code>last</code> 间的距离成线性。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<p>拥有名为 <code>ExecutionPolicy</code> 的模板形参的重载按下列方式报告错误：</p>
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<ul>
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<li>若作为算法一部分调用的函数的执行抛出异常，且 <code>ExecutionPolicy</code> 为<a href="cpp-algorithm-execution_policy_tag_t.html">标准策略</a>之一，则调用 <span class="t-lc"><a href="cpp-error-terminate.html">std::terminate</a></span> 。对于任何其他 <code>ExecutionPolicy</code> ，行为是实现定义的。</li>
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<li>若算法无法分配内存，则抛出 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 。</li>
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</ul>
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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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<p>参阅 <a rel="nofollow" class="external text" href="https://github.com/gcc-mirror/gcc/blob/14d8a5ae472ca5743016f37da2dd4770d83dea21/libstdc%2B%2B-v3/include/bits/stl_algo.h#L1440-L1455">libstdc++</a>、 <a rel="nofollow" class="external text" href="https://github.com/llvm/llvm-project/tree/f221d905b131158cbe3cbc4320d1ecd1376c3f22/libcxx/include/__algorithm/rotate_copy.h">libc++</a> 与 <a rel="nofollow" class="external text" href="https://github.com/microsoft/STL/blob/472161105d596192194d4715ccad307c6c163b4a/stl/inc/algorithm#L4438-L4459">MSVC STL</a> 中的实现。</p>
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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> ForwardIt, <span class="kw1">class</span> OutputIt<span class="sy1">></span>
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<span class="kw4">constexpr</span> <span class="co1">// C++20 起</span>
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OutputIt rotate_copy<span class="br0">(</span>ForwardIt first, ForwardIt n_first,
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ForwardIt last, OutputIt d_first<span class="br0">)</span>
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<span class="br0">{</span>
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d_first <span class="sy1">=</span> <a href="cpp-algorithm-copy.html"><span class="kw1582">std::<span class="me2">copy</span></span></a><span class="br0">(</span>n_first, last, d_first<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">return</span> <a href="cpp-algorithm-copy.html"><span class="kw1582">std::<span class="me2">copy</span></span></a><span class="br0">(</span>first, n_first, d_first<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></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 <vector></span>
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<span class="co2">#include <iostream></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-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> src <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">auto</span> pivot <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>src.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, src.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> dest<span class="br0">(</span>src.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">rotate_copy</span><span class="br0">(</span>src.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, pivot, src.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, dest.<span class="me1">begin</span><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">const</span> <span class="kw4">auto</span> <span class="sy3">&</span>i <span class="sy4">:</span> dest<span class="br0">)</span> <span class="br0">{</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> i <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
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<span class="br0">}</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> <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 4 5 1 2</pre></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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-rotate.html"><span class="t-lines"><span>rotate</span></span></a></div>
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</div>
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</td>
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<td>旋转范围中的元素顺序<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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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-rotate_copy.html"><span class="t-lines"><span>ranges::rotate_copy</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>复制并旋转元素范围<br />
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<span class="t-mark">(niebloid)</span></td>
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</div>
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<div class="visualClear"></div>
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