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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::bitset&lt;N&gt;::</span>count</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a>&lrm; | <a href="cpp-utility-bitset.html">bitset</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> count<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx11">(C++11 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> count<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#36820;&#22238;&#35774;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#30340;&#20301;&#25968;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#35774;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#30340;&#20301;&#25968;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;bitset&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1">&lt;</span><span class="nu0">8</span><span class="sy1">&gt;</span> b<span class="br0">(</span><span class="st0">&quot;00010010&quot;</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;initial value: &quot;</span> <span class="sy1">&lt;&lt;</span> b <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="co1">// &#23547;&#25214;&#39318;&#20010;&#26410;&#35774;&#32622;&#30340;&#20301;</span>
<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> idx <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
<span class="kw1">while</span> <span class="br0">(</span>idx <span class="sy1">&lt;</span> b.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> b.<span class="me1">test</span><span class="br0">(</span>idx<span class="br0">)</span><span class="br0">)</span> <span class="sy2">++</span>idx<span class="sy4">;</span>
<span class="co1">// &#32487;&#32493;&#35774;&#32622;&#20301;&#30452;&#33267; bitset &#26377;&#19968;&#21322;&#34987;&#22635;&#20805;</span>
<span class="kw1">while</span> <span class="br0">(</span>idx <span class="sy1">&lt;</span> b.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> b.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;</span> b.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy2">/</span><span class="nu0">2</span><span class="br0">)</span> <span class="br0">{</span>
b.<span class="me1">set</span><span class="br0">(</span>idx<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;setting bit &quot;</span> <span class="sy1">&lt;&lt;</span> idx <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;: &quot;</span> <span class="sy1">&lt;&lt;</span> b <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw1">while</span> <span class="br0">(</span>idx <span class="sy1">&lt;</span> b.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> b.<span class="me1">test</span><span class="br0">(</span>idx<span class="br0">)</span><span class="br0">)</span> <span class="sy2">++</span>idx<span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">initial value: 00010010
setting bit 0: 00010011
setting bit 2: 00010111</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-utility-bitset-size.html"><span class="t-lines"><span>size</span></span></a></div>
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<td>&#36820;&#22238;&#20301;&#38598;&#20445;&#26377;&#30340;&#20301;&#25968;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><a href="cpp-numeric-popcount.html"><span class="t-lines"><span>popcount</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>&#35745;&#37327;&#26080;&#31526;&#21495;&#25972;&#25968;&#20013;&#20026; 1 &#30340;&#20301;&#30340;&#25968;&#37327;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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