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<p>Implementation to <a href="https://www.geeksforgeeks.org/count-set-bits-in-an-integer/" target="_blank">count number of set bits of a number</a> in an integer.
<a href="#details">More...</a></p>
<div class="textblock"><code>#include &lt;cassert&gt;</code><br />
<code>#include &lt;iostream&gt;</code><br />
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Include dependency graph for count_of_set_bits.cpp:</div>
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<tr class="memitem:d7/d81/namespacebit__manipulation"><td class="memItemLeft" align="right" valign="top">namespace &#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d81/namespacebit__manipulation.html">bit_manipulation</a></td></tr>
<tr class="memdesc:d7/d81/namespacebit__manipulation"><td class="mdescLeft">&#160;</td><td class="mdescRight">for IO operations <br /></td></tr>
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<tr class="memitem:dd/dae/namespacecount__of__set__bits"><td class="memItemLeft" align="right" valign="top">namespace &#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../dd/dae/namespacecount__of__set__bits.html">count_of_set_bits</a></td></tr>
<tr class="memdesc:dd/dae/namespacecount__of__set__bits"><td class="mdescLeft">&#160;</td><td class="mdescRight">Functions for the <a href="https://www.geeksforgeeks.org/count-set-bits-in-an-integer/" target="_blank">count sets bits</a> implementation. <br /></td></tr>
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Functions</h2></td></tr>
<tr class="memitem:a86c98dc299e4db28b73e08309d977e62"><td class="memItemLeft" align="right" valign="top"><a class="elRef" target="_blank" href="http://en.cppreference.com/w/cpp/types/integer.html">std::uint64_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../da/db8/count__of__set__bits_8cpp.html#a86c98dc299e4db28b73e08309d977e62">bit_manipulation::count_of_set_bits::countSetBits</a> (std ::int64_t n)</td></tr>
<tr class="memdesc:a86c98dc299e4db28b73e08309d977e62"><td class="mdescLeft">&#160;</td><td class="mdescRight">The main function implements set bit count. <a href="../../da/db8/count__of__set__bits_8cpp.html#a86c98dc299e4db28b73e08309d977e62">More...</a><br /></td></tr>
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<tr class="memitem:aa8dca7b867074164d5f45b0f3851269d"><td class="memItemLeft" align="right" valign="top">static void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../da/db8/count__of__set__bits_8cpp.html#aa8dca7b867074164d5f45b0f3851269d">test</a> ()</td></tr>
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<tr class="memitem:ae66f6b31b5ad750f1fe042a706a4e3d4"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../da/db8/count__of__set__bits_8cpp.html#ae66f6b31b5ad750f1fe042a706a4e3d4">main</a> ()</td></tr>
<tr class="memdesc:ae66f6b31b5ad750f1fe042a706a4e3d4"><td class="mdescLeft">&#160;</td><td class="mdescRight">Main function. <a href="../../da/db8/count__of__set__bits_8cpp.html#ae66f6b31b5ad750f1fe042a706a4e3d4">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p >Implementation to <a href="https://www.geeksforgeeks.org/count-set-bits-in-an-integer/" target="_blank">count number of set bits of a number</a> in an integer. </p>
<p >We are given an integer number. We need to calculate the number of set bits in it.</p>
<p >A binary number consists of two digits. They are 0 &amp; 1. Digit 1 is known as set bit in computer terms. Worst Case Time Complexity: O(log n) Space complexity: O(1) </p><dl class="section author"><dt>Author</dt><dd><a href="https://github.com/Swastyy" target="_blank">Swastika Gupta</a> </dd>
<dd>
<a href="https://github.com/prashant-th18" target="_blank">Prashant Thakur</a> </dd></dl>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="a86c98dc299e4db28b73e08309d977e62" name="a86c98dc299e4db28b73e08309d977e62"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a86c98dc299e4db28b73e08309d977e62">&#9670;&nbsp;</a></span>countSetBits()</h2>
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<td class="memname"><a class="elRef" target="_blank" href="http://en.cppreference.com/w/cpp/types/integer.html">std::uint64_t</a> bit_manipulation::count_of_set_bits::countSetBits </td>
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<td class="paramtype">std ::int64_t&#160;</td>
<td class="paramname"><em>n</em></td><td>)</td>
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<p>The main function implements set bit count. </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">n</td><td>is the number whose set bit will be counted </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>total number of set-bits in the binary representation of number <code>n</code> </dd></dl>
<div class="fragment"><div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span> { <span class="comment">// int64_t is preferred over int so that</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span> <span class="comment">// no Overflow can be there.</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span> </div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span> <span class="keywordtype">int</span> count = 0; <span class="comment">// &quot;count&quot; variable is used to count number of set-bits(&#39;1&#39;) in</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span> <span class="comment">// binary representation of number &#39;n&#39;</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span> <span class="keywordflow">while</span> (n != 0)</div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno"> 42</span> {</div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno"> 43</span> ++count;</div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno"> 44</span> n = (n &amp; (n - 1));</div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno"> 45</span> }</div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno"> 46</span> <span class="keywordflow">return</span> count;</div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno"> 47</span> <span class="comment">// Why this algorithm is better than the standard one?</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno"> 48</span> <span class="comment">// Because this algorithm runs the same number of times as the number of</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno"> 49</span> <span class="comment">// set-bits in it. Means if my number is having &quot;3&quot; set bits, then this while loop</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno"> 50</span> <span class="comment">// will run only &quot;3&quot; times!!</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno"> 51</span>}</div>
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Here is the call graph for this function:</div>
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<h2 class="memtitle"><span class="permalink"><a href="#ae66f6b31b5ad750f1fe042a706a4e3d4">&#9670;&nbsp;</a></span>main()</h2>
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<td class="memname">int main </td>
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<p>Main function. </p>
<dl class="section return"><dt>Returns</dt><dd>0 on exit </dd></dl>
<div class="fragment"><div class="line"><a id="l00078" name="l00078"></a><span class="lineno"> 78</span> {</div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno"> 79</span> test(); <span class="comment">// run self-test implementations</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno"> 80</span> <span class="keywordflow">return</span> 0;</div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno"> 81</span>}</div>
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<h2 class="memtitle"><span class="permalink"><a href="#aa8dca7b867074164d5f45b0f3851269d">&#9670;&nbsp;</a></span>test()</h2>
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<td class="memname">static void test </td>
<td>(</td>
<td class="paramname"></td><td>)</td>
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<span class="mlabels"><span class="mlabel">static</span></span> </td>
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<div class="fragment"><div class="line"><a id="l00055" name="l00055"></a><span class="lineno"> 55</span> {</div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno"> 56</span> <span class="comment">// n = 4 return 1</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno"> 57</span> assert(bit_manipulation::count_of_set_bits::countSetBits(4) == 1);</div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno"> 58</span> <span class="comment">// n = 6 return 2</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno"> 59</span> assert(bit_manipulation::count_of_set_bits::countSetBits(6) == 2);</div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno"> 60</span> <span class="comment">// n = 13 return 3</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno"> 61</span> assert(bit_manipulation::count_of_set_bits::countSetBits(13) == 3);</div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno"> 62</span> <span class="comment">// n = 9 return 2</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno"> 63</span> assert(bit_manipulation::count_of_set_bits::countSetBits(9) == 2);</div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno"> 64</span> <span class="comment">// n = 15 return 4</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno"> 65</span> assert(bit_manipulation::count_of_set_bits::countSetBits(15) == 4);</div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno"> 66</span> <span class="comment">// n = 25 return 3</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno"> 67</span> assert(bit_manipulation::count_of_set_bits::countSetBits(25) == 3);</div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno"> 68</span> <span class="comment">// n = 97 return 3</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno"> 69</span> assert(bit_manipulation::count_of_set_bits::countSetBits(97) == 3);</div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno"> 70</span> <span class="comment">// n = 31 return 5</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno"> 71</span> assert(bit_manipulation::count_of_set_bits::countSetBits(31) == 5);</div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno"> 72</span> <a class="code hl_classRef" target="_blank" href="http://en.cppreference.com/w/cpp/io/basic_ostream.html">std::cout</a> &lt;&lt; <span class="stringliteral">&quot;All test cases successfully passed!&quot;</span> &lt;&lt; <a class="code hl_functionRef" target="_blank" href="http://en.cppreference.com/w/cpp/io/manip/endl.html">std::endl</a>;</div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno"> 73</span>}</div>
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