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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ranges::</span>max_element</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-algorithm.html">algorithm</a>&lrm; | <a href="cpp-algorithm-ranges.html">ranges</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-algorithm.html">&lt;algorithm&gt;</a></code></div>
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<div>&#35843;&#29992;&#31614;&#21517;</div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</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">&lt;</span>I<span class="sy1">&gt;</span> S, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,<br /></span>
<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1">&lt;</span>std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1">&lt;</span>I, Proj<span class="sy1">&gt;&gt;</span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span> <span class="sy1">&gt;</span><br /></p>
<span class="kw4">constexpr</span> I max_element<span class="br0">(</span> I first, S last, 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>(1)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> ranges<span class="sy4">::</span><span class="me2">forward_range</span> R, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,<br /></span>
<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1">&lt;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1">&lt;</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1">&lt;</span>R<span class="sy1">&gt;</span>, Proj<span class="sy1">&gt;&gt;</span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span> <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1">&lt;</span>R<span class="sy1">&gt;</span><br /></p>
max_element<span class="br0">(</span> R<span class="sy3">&amp;&amp;</span> r, 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>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> &#23547;&#25214;&#33539;&#22260; <code>[first, last)</code> &#20013;&#30340;&#26368;&#22823;&#20803;&#32032;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#21516; <span class="t-v">(1)</span> &#65292;&#20294;&#20197; <code>r</code> &#20026;&#28304;&#33539;&#22260;&#65292;&#22914;&#21516;&#20197; <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> &#20026; <code>first</code> &#24182;&#20197; <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> &#20026; <code>last</code> &#12290;</div>
<p>&#27492;&#39029;&#38754;&#19978;&#25551;&#36848;&#30340;&#20223;&#20989;&#25968;&#23454;&#20307;&#26159; <i>niebloid</i> &#65292;&#21363;&#65306;</p>
<ul>
<li>&#35843;&#29992;&#23427;&#20204;&#20013;&#30340;&#20219;&#20309;&#19968;&#32773;&#26102;&#19981;&#21487;&#25351;&#23450;&#26174;&#24335;&#27169;&#26495;&#23454;&#21442;&#12290;</li>
<li>&#23427;&#20204;&#26080;&#19968;&#23545;<a href="cpp-language-adl.html">&#23454;&#21442;&#20381;&#36182;&#26597;&#25214;</a>&#21487;&#35265;&#12290;</li>
<li>&#22312;<a href="cpp-language-unqualified_lookup.html">&#36890;&#24120;&#26080;&#38480;&#23450;&#26597;&#25214;</a>&#23547;&#25214;&#20989;&#25968;&#35843;&#29992;&#36816;&#31639;&#31526;&#24038;&#20391;&#30340;&#21517;&#31216;&#25214;&#21040;&#23427;&#20204;&#20043;&#19968;&#26102;&#65292;&#23427;&#31105;&#27490;<a href="cpp-language-adl.html">&#23454;&#21442;&#20381;&#36182;&#26597;&#25214;</a>&#12290;</li>
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<p>&#23454;&#38469;&#19978;&#65292;&#23427;&#20204;&#33021;&#20197;&#20989;&#25968;&#23545;&#35937;&#65292;&#25110;&#20197;&#26576;&#20123;&#29305;&#27530;&#32534;&#35793;&#22120;&#25193;&#23637;&#23454;&#29616;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>first, last</td>
<td>-</td>
<td>&#20195;&#34920;&#24453;&#26816;&#39564;&#33539;&#22260;&#30340;&#36845;&#20195;&#22120;-&#21736;&#20301;&#23545;</td>
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<td>r</td>
<td>-</td>
<td>&#24453;&#26816;&#39564;&#30340;&#33539;&#22260;</td>
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<td>comp</td>
<td>-</td>
<td>&#24212;&#29992;&#21040;&#25237;&#24433;&#21518;&#20803;&#32032;&#30340;&#27604;&#36739;</td>
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<td>proj</td>
<td>-</td>
<td>&#24212;&#29992;&#21040;&#20803;&#32032;&#30340;&#25237;&#24433;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#25351;&#21521;&#33539;&#22260; <code>[first, last)</code> &#20013;&#26368;&#22823;&#20803;&#32032;&#30340;&#36845;&#20195;&#22120;&#12290;&#33509;&#33539;&#22260;&#20013;&#25968;&#20010;&#20803;&#32032;&#31561;&#20215;&#20110;&#26368;&#22823;&#20803;&#32032;&#65292;&#21017;&#36820;&#22238;&#25351;&#21521;&#39318;&#20010;&#36825;&#31181;&#20803;&#32032;&#30340;&#36845;&#20195;&#22120;&#12290;&#33509;&#33539;&#22260;&#20026;&#31354;&#21017;&#36820;&#22238; <code>first</code> &#12290;</p>
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">&#22797;&#26434;&#24230;</span></h3>
<p>&#20934;&#30830;&#27604;&#36739; <span class="texhtml" style="white-space: nowrap;">max(N-1,0)</span> &#27425;&#65292;&#20854;&#20013; <span class="t-c"><span class="mw-geshi cpp source-cpp">N <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></span> &#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">&#21487;&#33021;&#30340;&#23454;&#29616;</span></h3>
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<pre class="de1"><span class="kw1">struct</span> max_element_fn <span class="br0">{</span>
<span class="kw1">template</span><span class="sy1">&lt;</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">&lt;</span>I<span class="sy1">&gt;</span> S, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,
std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1">&lt;</span>std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1">&lt;</span>I, Proj<span class="sy1">&gt;&gt;</span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span><span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> I operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>I first, S last, 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>
<span class="br0">{</span>
<span class="kw1">if</span> <span class="br0">(</span>first <span class="sy1">==</span> last<span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">return</span> last<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">auto</span> largest <span class="sy1">=</span> first<span class="sy4">;</span>
<span class="sy2">++</span>first<span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> first <span class="sy3">!</span><span class="sy1">=</span> last<span class="sy4">;</span> <span class="sy2">++</span>first<span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">if</span> <span class="br0">(</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>comp, <a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>proj, <span class="sy2">*</span>largest<span class="br0">)</span>, <a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>proj, <span class="sy2">*</span>first<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
largest <span class="sy1">=</span> first<span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="kw1">return</span> largest<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">template</span><span class="sy1">&lt;</span>ranges<span class="sy4">::</span><span class="me2">forward_range</span> R, <span class="kw1">class</span> Proj <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,
std<span class="sy4">::</span><span class="me2">indirect_strict_weak_order</span><span class="sy1">&lt;</span>
std<span class="sy4">::</span><span class="me2">projected</span><span class="sy1">&lt;</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1">&lt;</span>R<span class="sy1">&gt;</span>, Proj<span class="sy1">&gt;&gt;</span> Comp <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">less</span><span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1">&lt;</span>R<span class="sy1">&gt;</span>
operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>R<span class="sy3">&amp;&amp;</span> r, 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>
<span class="br0">{</span>
<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>, <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>
<span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">inline</span> <span class="kw4">constexpr</span> max_element_fn max_element<span class="sy4">;</span></pre></div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<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 &lt;algorithm&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;vector&gt;</span>
<span class="co2">#include &lt;cmath&gt;</span>
<span class="kw4">static</span> <span class="kw4">bool</span> abs_compare<span class="br0">(</span><span class="kw4">int</span> a, <span class="kw4">int</span> b<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">return</span> <span class="br0">(</span>std<span class="sy4">::</span><span class="me2">abs</span><span class="br0">(</span>a<span class="br0">)</span> <span class="sy1">&lt;</span> std<span class="sy4">::</span><span class="me2">abs</span><span class="br0">(</span>b<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> v<span class="br0">{</span> <span class="nu0">3</span>, <span class="nu0">1</span>, <span class="sy2">-</span><span class="nu0">14</span>, <span class="nu0">1</span>, <span class="nu0">5</span>, <span class="nu0">9</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">namespace</span> ranges <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">;</span>
<span class="kw4">auto</span> result <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">max_element</span><span class="br0">(</span>v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, v.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;max element at: &quot;</span> <span class="sy1">&lt;&lt;</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, result<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
result <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">max_element</span><span class="br0">(</span>v, abs_compare<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;max element (absolute) at: &quot;</span> <span class="sy1">&lt;&lt;</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, result<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">max element at: 5
max element (absolute) at: 2</pre></div>
</div>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-algorithm-ranges-min_element.html"><span class="t-lines"><span>ranges::min_element</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#36820;&#22238;&#33539;&#22260;&#20013;&#30340;&#26368;&#23567;&#20803;&#32032;<br />
<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-minmax_element.html"><span class="t-lines"><span>ranges::minmax_element</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#36820;&#22238;&#33539;&#22260;&#20013;&#30340;&#26368;&#23567;&#21644;&#26368;&#22823;&#20803;&#32032;<br />
<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-max.html"><span class="t-lines"><span>ranges::max</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#36820;&#22238;&#32473;&#23450;&#20540;&#30340;&#36739;&#22823;&#32773;<br />
<span class="t-mark">(niebloid)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-algorithm-max_element.html"><span class="t-lines"><span>max_element</span></span></a></div>
</div>
</td>
<td>&#36820;&#22238;&#33539;&#22260;&#20869;&#30340;&#26368;&#22823;&#20803;&#32032;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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