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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head>  <meta name="generator" content=  "HTML Tidy for Linux/x86 (vers 1 September 2005), see www.w3.org">  <title>count_if</title>  <link href="../cppreference.css" rel="stylesheet" type="text/css"></head><body><table>  <tr>  <td>  <div class="body-content">  <div class="header-box">    <a href="../index.html">cppreference.com</a> &gt; <a href=    "index.html">C++ Algorithms</a> &gt; <a href=    "count_if.html">count_if</a>  </div>  <div class="name-format">    count_if  </div>  <div class="syntax-name-format">    Syntax:  </div>  <pre class="syntax-box">  #include &lt;algorithm&gt;  size_t count_if( iterator start, iterator end, UnaryPred p );</pre>  <p>The count_if() function returns the number of elements between  <em>start</em> and <em>end</em> for which the predicate <em>p</em>  returns true.</p>  <p>For example, the following code uses count_if() with a predicate  that returns true for the integer 3 to count the number of items in  an array that are equal to 3:</p>  <pre class="example-code"> int nums[] = { 0, 1, 2, 3, 4, 5, 9, 3, 13 }; int start = 0; int end = 9;            int target_value = 3; int num_items = count_if( nums+start,                    nums+end,                    bind2nd(equal_to&lt;int&gt;(), target_value) );              cout &lt;&lt; &quot;nums[] contains &quot; &lt;&lt; num_items &lt;&lt; &quot; items matching &quot; &lt;&lt; target_value &lt;&lt; endl;               </pre>  <p>When run, the above code displays the following output:</p>  <pre class="example-code"> nums[] contains 2 items matching 3             </pre>  <div class="related-name-format">    Related topics:  </div>  <div class="related-content">    <a href="count.html">count</a>  </div>  </div>  </td>    </tr>  </table></body></html>

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