151 lines
11 KiB
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151 lines
11 KiB
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<title>std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>::equal_range</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_container_unordered_multimap_equal_range skin-cppreference2 action-view cpp-page-template cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>::</span>equal_range</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-container.html">container</a>‎ | <a href="cpp-container-unordered_multimap.html">unordered multimap</a></span></div>
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<div class="t-page-template" style="">
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<p></p>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>iterator,iterator<span class="sy1">></span> equal_range<span class="br0">(</span> <span class="kw4">const</span> Key<span class="sy3">&</span> key <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>const_iterator,const_iterator<span class="sy1">></span> equal_range<span class="br0">(</span> <span class="kw4">const</span> Key<span class="sy3">&</span> key <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 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> K <span class="sy1">></span><br />
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<a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>iterator,iterator<span class="sy1">></span> equal_range<span class="br0">(</span> <span class="kw4">const</span> K<span class="sy3">&</span> x <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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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> K <span class="sy1">></span><br />
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<a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>const_iterator,const_iterator<span class="sy1">></span> equal_range<span class="br0">(</span> <span class="kw4">const</span> K<span class="sy3">&</span> x <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td>(4)</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">1,2)</span> 返回容器中所有键等于 <code>key</code> 的元素范围。范围以二个迭代器定义，第一个指向所需范围的首元素，而第二个指向范围的尾后一位元素。</div>
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<div class="t-li1"><span class="t-li">3,4)</span> 返回含有容器中所有键等价于 <code>x</code> 的元素的范围。此重载仅若有限定标识 <span class="t-c"><span class="mw-geshi cpp source-cpp">Hash<span class="sy4">::</span><span class="me2">is_transparent</span></span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp">KeyEqual<span class="sy4">::</span><span class="me2">is_transparent</span></span></span> 均合法并指代类型才参与重载决议。这假设能用 <code>K</code> 和 <code>Key</code> 类型一起调用这种 <code>Hash</code> ，还有 <code>KeyEqual</code> 是通透的，进而允许不用构造 <code>Key</code> 的实例就调用此函数。</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>key</td>
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<td>-</td>
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<td>要与元素比较的键值</td>
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</tr>
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<tr class="t-par">
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<td>x</td>
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<td>-</td>
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<td>任何能与键通透比较的类型的值</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>含一对定义所需范围的迭代器的 <span class="t-lc"><a href="cpp-utility-pair.html">std::pair</a></span> 。若无这种元素，则将尾后（见 <span class="t-lc"><a href="cpp-container-unordered_multimap-end.html">end()</a></span> ）迭代器作为 pair 的两个元素返回。</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>平均情况与带关键 <code>key</code> 的元素数成线性，最坏情况与容器大小成线性。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example-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 <unordered_map></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-unordered_multimap.html"><span class="kw1295">std::<span class="me2">unordered_multimap</span></span></a><span class="sy1"><</span><span class="kw4">int</span>,<span class="kw4">char</span><span class="sy1">></span> map <span class="sy1">=</span> <span class="br0">{</span><span class="br0">{</span><span class="nu0">1</span>,<span class="st0">'a'</span><span class="br0">}</span>,<span class="br0">{</span><span class="nu0">1</span>,<span class="st0">'b'</span><span class="br0">}</span>,<span class="br0">{</span><span class="nu0">1</span>,<span class="st0">'d'</span><span class="br0">}</span>,<span class="br0">{</span><span class="nu0">2</span>,<span class="st0">'b'</span><span class="br0">}</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">auto</span> range <span class="sy1">=</span> map.<span class="me1">equal_range</span><span class="br0">(</span><span class="nu0">1</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">auto</span> it <span class="sy1">=</span> range.<span class="me1">first</span><span class="sy4">;</span> it <span class="sy3">!</span><span class="sy1">=</span> range.<span class="me1">second</span><span class="sy4">;</span> <span class="sy2">++</span>it<span class="br0">)</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> it<span class="sy2">-</span><span class="sy1">></span>first <span class="sy1"><<</span> <span class="st0">' '</span> <span class="sy1"><<</span> it<span class="sy2">-</span><span class="sy1">></span>second <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="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">1 a
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1 b
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1 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-container-unordered_multimap-find.html"><span class="t-lines"><span>find</span></span></a></div>
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<div><span class="t-lines"><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>寻找带有特定键的元素<br />
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<span class="t-mark">(公开成员函数)</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-container-unordered_multimap-contains.html"><span class="t-lines"><span>contains</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>检查容器是否含有带特定键的元素<br />
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<span class="t-mark">(公开成员函数)</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-container-unordered_multimap-count.html"><span class="t-lines"><span>count</span></span></a></div>
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<div><span class="t-lines"><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>返回匹配特定键的元素数量<br />
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<span class="t-mark">(公开成员函数)</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-equal_range.html"><span class="t-lines"><span>equal_range</span></span></a></div>
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</div>
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</td>
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<td>返回匹配特定键值的元素范围<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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