405 lines
33 KiB
HTML
405 lines
33 KiB
HTML
<!DOCTYPE html>
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<title>std::equal</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_equal skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>equal</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></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></td>
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<td></td>
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<td rowspan="142">(1)</td>
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<td></td>
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<tr class="t-dcl 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> InputIt1, <span class="kw1">class</span> InputIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
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InputIt2 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-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> InputIt1, <span class="kw1">class</span> InputIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
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InputIt2 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>
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<tr class="t-dcl t-since-cxx17">
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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><span class="kw4">bool</span> equal<span class="br0">(</span> ExecutionPolicy<span class="sy3">&&</span> policy, 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>(2)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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</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">(3)</td>
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<td></td>
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<tr class="t-dcl 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> InputIt1, <span class="kw1">class</span> InputIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
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InputIt2 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-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> InputIt1, <span class="kw1">class</span> InputIt2, <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> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
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InputIt2 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>
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<tr class="t-dcl t-since-cxx17">
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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,<br /></span>
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<p> <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br />
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<span class="kw4">bool</span> equal<span class="br0">(</span> ExecutionPolicy<span class="sy3">&&</span> policy, 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>(4)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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</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">(5)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx14 t-until-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> InputIt1, <span class="kw1">class</span> InputIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
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InputIt2 first2, InputIt2 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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<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> InputIt1, <span class="kw1">class</span> InputIt2 <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> <span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
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InputIt2 first2, InputIt2 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>
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<tr class="t-dcl t-since-cxx17">
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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> ExecutionPolicy, <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> equal<span class="br0">(</span> ExecutionPolicy<span class="sy3">&&</span> policy, 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>(6)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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</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">(7)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx14 t-until-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> InputIt1, <span class="kw1">class</span> InputIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br /></span>
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<p><span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br />
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InputIt2 first2, InputIt2 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> InputIt1, <span class="kw1">class</span> InputIt2, <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> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br />
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InputIt2 first2, InputIt2 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 t-since-cxx17">
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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> ExecutionPolicy, <span class="kw1">class</span> ForwardIt1, <span class="kw1">class</span> ForwardIt2,<br /></span>
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<p> <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span><br />
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<span class="kw4">bool</span> equal<span class="br0">(</span> ExecutionPolicy<span class="sy3">&&</span> policy, 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>(8)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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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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</table>
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<div class="t-li1"><span class="t-li">1,3)</span> 如果范围 <code>[first1, last1)</code> 和范围 <code>[first2, first2 + (last1 - first1))</code> 相等，返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，否则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span></div>
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<div class="t-li1"><span class="t-li">5,7)</span> 如果范围 <code>[first1, last1)</code> 和范围 <code>[first2, last2)</code> 相等，返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，否则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span></div>
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<div class="t-li1"><span class="t-li">2,4,6,8)</span> 同 <span class="t-v">(1,3,5,7)</span> ，但按照 <code>policy</code> 执行。这些重载仅若 <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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<p>两个范围相等的条件是：对于范围 <code>[first1, last1)</code> 内的每个迭代器 <code>i</code> ， <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>i</span></span> 等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span><span class="br0">(</span>first2 <span class="sy2">+</span> <span class="br0">(</span>i <span class="sy2">-</span> first1<span class="br0">)</span><span class="br0">)</span></span></span> 。重载形式 <span class="t-v">(1,2,5,6)</span> 用 <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="sy1">==</span></span></span> 判定两个元素是否相等，而重载形式 <span class="t-v">(3,4,7,8)</span> 用给定的谓词函数。</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>first1, last1</td>
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<td>-</td>
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<td>进行比较的第一个范围</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>进行比较的第二个范围</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>若元素应被当做相等则返回 ​<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> Type1 <span class="sy3">&</span>a, <span class="kw4">const</span> Type2 <span class="sy3">&</span>b<span class="br0">)</span><span class="sy4">;</span></span></span></p>
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<p>虽然签名不必有 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <span class="sy3">&</span></span></span> ，函数也不能修改传递给它的对象，而且必须接受（可为 const 的）类型 <code>Type1</code> 与 <code>Type2</code> 的值，无关乎<a href="cpp-language-value_category.html">值类别</a>（从而不允许 <span class="t-c"><span class="mw-geshi cpp source-cpp">Type1 <span class="sy3">&</span></span></span> <span class="t-rev-inl t-since-cxx11"><span>，亦不允许 <span class="t-c"><span class="mw-geshi cpp source-cpp">Type1</span></span> ，除非 <code>Type1</code> 的移动等价于复制</span> <span><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></span></span>）。<br />
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类型 <span class="t-c"><span class="mw-geshi cpp source-cpp">Type1</span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp">Type2</span></span> 必须使得 <span class="t-c"><span class="mw-geshi cpp source-cpp">InputIt1</span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp">InputIt2</span></span> 类型的对象在解引用后分别能隐式转换到 <span class="t-c"><span class="mw-geshi cpp source-cpp">Type1</span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp">Type2</span></span> 。 ​</p>
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</td>
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</tr>
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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>InputIt1, InputIt2</code> 必须满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> 的要求。</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">5-8)</span> 如果范围 <code>[first1, last1)</code> 的长度不等于范围 <code>[first2, last2)</code> 的长度则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 。</div>
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<p>如果两个范围内的元素都相等，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 。</p>
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<p>否则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 。</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><code>std::equal</code> 不可应用到由 <span class="t-lc"><a href="cpp-container-unordered_set.html">std::unordered_set</a></span> 、 <span class="t-lc"><a href="cpp-container-unordered_multiset.html">std::unordered_multiset</a></span> 、 <span class="t-lc"><a href="cpp-container-unordered_map.html">std::unordered_map</a></span> 或 <span class="t-lc"><a href="cpp-container-unordered_multimap.html">std::unordered_multimap</a></span> 的迭代器构成的范围，因为即使此类容器存储相同的元素，在容器内元素存储的顺序也可能不同。</p>
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<p>比较整个容器是否相等时，针对该容器的 <code>operator==</code> 重载通常是更好的选择。</p>
|
|
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
|
|
<div class="t-li1"><span class="t-li">1,2)</span> 最多 <code>last1</code> - <code>first1</code> 次调用相应的谓词函数。</div>
|
|
<div class="t-li1"><span class="t-li">3,4)</span> 最多 min(<code>last1</code> - <code>first1</code>, <code>last2</code> - <code>first2</code>) 次调用相应的谓词函数。</div>
|
|
<p>然而，若 <code>InputIt1</code> 和 <code>InputIt2</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">last1 <span class="sy2">-</span> first1 <span class="sy3">!</span><span class="sy1">=</span> last2 <span class="sy2">-</span> first2</span></span> 则不调用谓词函数。</p>
|
|
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
|
|
<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>
|
|
<ul>
|
|
<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>
|
|
<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>
|
|
</ul>
|
|
<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>
|
|
<table class="eq-fun-cpp-table">
|
|
<tr>
|
|
<th>版本一</th>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> InputIt1, <span class="kw1">class</span> InputIt2<span class="sy1">></span>
|
|
<span class="kw4">bool</span> equal<span class="br0">(</span>InputIt1 first1, InputIt1 last1,
|
|
InputIt2 first2<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> first1 <span class="sy3">!</span><span class="sy1">=</span> last1<span class="sy4">;</span> <span class="sy2">++</span>first1, <span class="sy2">++</span>first2<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span><span class="sy3">!</span><span class="br0">(</span><span class="sy2">*</span>first1 <span class="sy1">==</span> <span class="sy2">*</span>first2<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span>
|
|
<span class="kw1">return</span> <span class="kw2">true</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<th>版本二</th>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> InputIt1, <span class="kw1">class</span> InputIt2, <span class="kw1">class</span> BinaryPredicate<span class="sy1">></span>
|
|
<span class="kw4">bool</span> equal<span class="br0">(</span>InputIt1 first1, InputIt1 last1,
|
|
InputIt2 first2, BinaryPredicate p<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> first1 <span class="sy3">!</span><span class="sy1">=</span> last1<span class="sy4">;</span> <span class="sy2">++</span>first1, <span class="sy2">++</span>first2<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span><span class="sy3">!</span>p<span class="br0">(</span><span class="sy2">*</span>first1, <span class="sy2">*</span>first2<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span>
|
|
<span class="kw1">return</span> <span class="kw2">true</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<th>版本三</th>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> InputIt1, <span class="kw1">class</span> InputIt2<span class="sy1">></span>
|
|
<span class="kw4">bool</span> equal<span class="br0">(</span>InputIt1 first1, InputIt1 last1,
|
|
InputIt2 first2, InputIt2 last2 <span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span>distance<span class="br0">(</span>first1,last1<span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> distance<span class="br0">(</span>first2,last2<span class="br0">)</span>
|
|
<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> first1 <span class="sy3">!</span><span class="sy1">=</span> last1, first2 <span class="sy3">!</span><span class="sy1">=</span> last2<span class="sy4">;</span> <span class="sy2">++</span>first1, <span class="sy2">++</span>first2<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span><span class="sy3">!</span><span class="br0">(</span><span class="sy2">*</span>first1 <span class="sy1">==</span> <span class="sy2">*</span>first2<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span>
|
|
<span class="kw1">return</span> <span class="kw2">true</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<th>版本四</th>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> InputIt1, <span class="kw1">class</span> InputIt2, <span class="kw1">class</span> BinaryPredicate <span class="sy1">></span>
|
|
<span class="kw4">bool</span> equal<span class="br0">(</span> InputIt1 first1, InputIt1 last1,
|
|
InputIt2 first2, InputIt2 last2,
|
|
BinaryPredicate p <span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span>distance<span class="br0">(</span>first1,last1<span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> distance<span class="br0">(</span>first2,last2<span class="br0">)</span>
|
|
<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> first1 <span class="sy3">!</span><span class="sy1">=</span> last1, first2 <span class="sy3">!</span><span class="sy1">=</span> last2<span class="sy4">;</span> <span class="sy2">++</span>first1, <span class="sy2">++</span>first2<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span><span class="sy3">!</span>p<span class="br0">(</span><span class="sy2">*</span>first1, <span class="sy2">*</span>first2<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span>
|
|
<span class="kw1">return</span> <span class="kw2">true</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<p>下面的代码使用 <code>equal()</code> 来测试字符串是否是回文</p>
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <algorithm></span>
|
|
<span class="co2">#include <string></span>
|
|
|
|
<span class="kw4">void</span> test<span class="br0">(</span><span class="kw4">const</span> <a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="sy3">&</span> s<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">if</span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">equal</span><span class="br0">(</span>s.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, s.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">+</span> s.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy2">/</span><span class="nu0">2</span>, s.<span class="me1">rbegin</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<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">\"</span>"</span> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span> is a palindrome<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</span>
|
|
<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">\"</span>"</span> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span> is not a palindrome<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span>
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
test<span class="br0">(</span><span class="st0">"radar"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
test<span class="br0">(</span><span class="st0">"hello"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">"radar" is a palindrome
|
|
"hello" is not a palindrome</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-find.html"><span class="t-lines"><span>find</span><span>find_if</span><span>find_if_not</span></span></a></div>
|
|
<div><span class="t-lines"><span></span><span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找首个满足特定判别标准的元素<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-lexicographical_compare.html"><span class="t-lines"><span>lexicographical_compare</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>当一个范围按字典顺序小于另一个范围时，返回 true<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-mismatch.html"><span class="t-lines"><span>mismatch</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找两个范围出现不同的首个位置<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-search.html"><span class="t-lines"><span>search</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>搜索一个元素范围<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|