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<span class="bchead">You are here: </span><a href="../../start.html" title="start">C++ Reference</a> » <a href="../../stl/start.html" title="stl:start">C++ Standard Template Library</a> » <a href="../../stl/set/start.html" title="stl:set:start">C++ Sets</a> » <a href="../../stl/set/count.html" title="stl:set:count">count</a> </div>
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<h2><a name="count" id="count">count</a></h2>
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<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <set></span>
size_type count<span class="br0">(</span> <span class="kw4">const</span> key_type<span class="sy0">&</span> key <span class="br0">)</span> <span class="kw4">const</span><span class="sy0">;</span></pre>
<p>
The function count() returns the number of occurrences of key in the set, which is always 0 or 1.
count() should run in <a href="../../complexity.html" class="wikilink1" title="complexity">logarithmic time</a>.
</p>
<p>
For example, the following code uses count() to determine if elements are contained in the set:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co1">// Create a set of characters</span>
set<span class="sy0"><</span>char<span class="sy0">></span> charSet<span class="sy0">;</span>
<span class="kw4">const</span> <span class="kw4">char</span><span class="sy0">*</span> s <span class="sy0">=</span> <span class="st0">"Hello There"</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">int</span> i<span class="sy0">=</span><span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> strlen<span class="br0">(</span>s<span class="br0">)</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <span class="br0">{</span>
charSet.<span class="me1">insert</span><span class="br0">(</span> s<span class="br0">[</span>i<span class="br0">]</span> <span class="br0">)</span><span class="sy0">;</span>
<span class="br0">}</span>
<span class="co1">// Display the set</span>
<span class="co1">// output is "01" (the characters in the set are " HTehlor")</span></pre>
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