248 lines
22 KiB
HTML
248 lines
22 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::ranges::upper_bound</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_ranges_upper_bound 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::ranges::</span>upper_bound</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-algorithm.html">algorithm</a>‎ | <a href="cpp-algorithm-ranges.html">ranges</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-algorithm.html"><algorithm></a></code></div>
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<div>调用签名</div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> std<span class="sy4">::</span><span class="me2">forward_iterator</span> I, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I<span class="sy1">></span> S,<br /></span>
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<p> <span class="kw1">class</span> T, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,<br />
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std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1"><</span><br />
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<span class="kw4">const</span> T<span class="sy2">*</span>,<br />
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std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1"><</span>I, Proj<span class="sy1">>></span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span> <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> I<br /></p>
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upper_bound<span class="br0">(</span> I first, S last, <span class="kw4">const</span> T<span class="sy3">&</span> value, Comp comp <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj proj <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span> <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> ranges<span class="sy4">::</span><span class="me2">forward_range</span> R, <span class="kw1">class</span> T, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,<br /></span>
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<p> std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1"><</span><br />
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<span class="kw4">const</span> T<span class="sy2">*</span>,<br />
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std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>, Proj<span class="sy1">>></span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span> <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span><br /></p>
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upper_bound<span class="br0">(</span> R<span class="sy3">&&</span> r, <span class="kw4">const</span> T<span class="sy3">&</span> value, Comp comp <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj proj <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span> <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-cxx20">(C++20 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 返回指向范围 <code>[first, last)</code> 中首个<i>大于</i> <code>value</code> 的元素的迭代器，或若找不到这种元素返回 <code>last</code> 。 范围 <code>[first, last)</code> 必须已按照表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>comp<span class="br0">(</span>value, element<span class="br0">)</span></span></span> 划分，即所有该表达式对其为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 的元素必须前趋所有该表达式对其为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 的元素。完全排序的范围符合此判别标准。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，但以 <code>r</code> 为源范围，如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 为 <code>first</code> 并以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 为 <code>last</code> 。</div>
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<p>此页面上描述的仿函数实体是 <i>niebloid</i> ，即：</p>
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<ul>
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<li>调用它们中的任何一者时不可指定显式模板实参。</li>
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<li>它们无一对<a href="cpp-language-adl.html">实参依赖查找</a>可见。</li>
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<li>在<a href="cpp-language-unqualified_lookup.html">通常无限定查找</a>寻找函数调用运算符左侧的名称找到它们之一时，它禁止<a href="cpp-language-adl.html">实参依赖查找</a>。</li>
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</ul>
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<p>实际上，它们能以函数对象，或以某些特殊编译器扩展实现。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>first, last</td>
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<td>-</td>
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<td>定义要检验的部分有序范围的迭代器-哨位对</td>
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<tr class="t-par">
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<td>r</td>
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<td>-</td>
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<td>要检验的部分有序范围</td>
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</tr>
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<tr class="t-par">
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<td>value</td>
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<td>-</td>
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<td>要与元素比较的值</td>
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<tr class="t-par">
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<td>pred</td>
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<td>-</td>
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<td>应用到投影后元素的谓词</td>
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<td>proj</td>
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<td>-</td>
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<td>应用到元素的投影</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>指向首个<i>大于</i> <code>value</code> 的元素的迭代器，或若找不到这种元素则为 <code>last</code> 。</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>比较和应用投影的次数与 <code>first</code> 和 <code>last</code> 之间的距离成对数（至多比较和应用投影 <span class="texhtml" style="white-space: nowrap;">log<span class="t-su t-su-b"><br />
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2</span>(last - first) + O(1)</span> 次）。然而，对于不实现 <a href="cpp-iterator-random_access_iterator.html"><code>random_access_iterator</code></a> 的迭代器，迭代器自增次数为线性。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<table class="eq-fun-cpp-table">
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="kw1">struct</span> upper_bound_fn <span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">forward_iterator</span> I, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I<span class="sy1">></span> S,
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<span class="kw1">class</span> T, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,
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std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1"><</span>
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<span class="kw4">const</span> T<span class="sy2">*</span>,
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std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1"><</span>I, Proj<span class="sy1">>></span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span><span class="sy1">></span>
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<span class="kw4">constexpr</span> I operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span> I first, S last, <span class="kw4">const</span> T<span class="sy3">&</span> value,
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Comp comp <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj proj <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span> <span class="br0">)</span> <span class="kw4">const</span>
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<span class="br0">{</span>
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I it<span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">iter_difference_t</span><span class="sy1"><</span>I<span class="sy1">></span> count, step<span class="sy4">;</span>
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count <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>first, last<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">while</span> <span class="br0">(</span>count <span class="sy1">></span> <span class="nu0">0</span><span class="br0">)</span> <span class="br0">{</span>
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it <span class="sy1">=</span> first<span class="sy4">;</span>
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step <span class="sy1">=</span> count <span class="sy2">/</span> <span class="nu0">2</span><span class="sy4">;</span>
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ranges<span class="sy4">::</span><span class="me2">advance</span><span class="br0">(</span>it, step, last<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span><span class="sy3">!</span>comp<span class="br0">(</span>value, <span class="sy2">*</span>it<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
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first <span class="sy1">=</span> <span class="sy2">++</span>it<span class="sy4">;</span>
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count <span class="sy2">-</span><span class="sy1">=</span> step <span class="sy2">+</span> <span class="nu0">1</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">else</span> <span class="br0">{</span>
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count <span class="sy1">=</span> step<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="kw1">return</span> first<span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">forward_range</span> R, <span class="kw1">class</span> T, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,
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std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1"><</span>
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<span class="kw4">const</span> T<span class="sy2">*</span>,
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std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>, Proj<span class="sy1">>></span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span><span class="sy1">></span>
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span> R<span class="sy3">&&</span> r, <span class="kw4">const</span> T<span class="sy3">&</span> value, Comp comp <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj proj <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span> <span class="br0">)</span> <span class="kw4">const</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span><span class="br0">(</span>ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r<span class="br0">)</span>, ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r<span class="br0">)</span>, value,
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<a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>comp<span class="br0">)</span>, <a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>proj<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">inline</span> <span class="kw4">constexpr</span> upper_bound_fn upper_bound<span class="sy4">;</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 <iostream></span>
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<span class="co2">#include <iterator></span>
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<span class="co2">#include <vector></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> data <span class="sy1">=</span> <span class="br0">{</span> <span class="nu0">1</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">3</span>, <span class="nu0">3</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">4</span>, <span class="nu0">4</span>, <span class="nu0">5</span>, <span class="nu0">5</span>, <span class="nu0">6</span> <span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">{</span>
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<span class="kw4">auto</span> lower <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">lower_bound</span><span class="br0">(</span>data.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, data.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">auto</span> upper <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">upper_bound</span><span class="br0">(</span>data.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, data.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
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ranges<span class="sy4">::</span><span class="me2">copy</span><span class="br0">(</span>lower, upper, <a href="cpp-iterator-ostream_iterator.html"><span class="kw670">std::<span class="me2">ostream_iterator</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>, <span class="st0">" "</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">{</span>
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<span class="kw4">auto</span> lower <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">lower_bound</span><span class="br0">(</span>data, <span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">auto</span> upper <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">upper_bound</span><span class="br0">(</span>data, <span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>
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ranges<span class="sy4">::</span><span class="me2">copy</span><span class="br0">(</span>lower, upper, <a href="cpp-iterator-ostream_iterator.html"><span class="kw670">std::<span class="me2">ostream_iterator</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>, <span class="st0">" "</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="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">4 4 4
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3 3 3 3</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-equal_range.html"><span class="t-lines"><span>ranges::equal_ranges</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>返回匹配特定值的元素范围<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-lower_bound.html"><span class="t-lines"><span>ranges::lower_bound</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>返回指向首个<i>不小于</i>给定值的元素的迭代器<br />
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<span class="t-mark">(niebloid)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-ranges-partition.html"><span class="t-lines"><span>ranges::partition</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>将范围中的元素分为二组<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
|
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<tr class="t-dsc">
|
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<td>
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<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-upper_bound.html"><span class="t-lines"><span>upper_bound</span></span></a></div>
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</div>
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</td>
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<td>返回指向第一个<i>大于</i>给定值的元素的迭代器<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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