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<div class="headertitle"><div class="title">count_of_set_bits.cpp File Reference</div></div>
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<p>Implementation to [count number of set bits of a number] (<a href="https://www.geeksforgeeks.org/count-set-bits-in-an-integer/">https://www.geeksforgeeks.org/count-set-bits-in-an-integer/</a>) in an integer.
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<a href="#details">More...</a></p>
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<div class="textblock"><code>#include <cassert></code><br />
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<code>#include <cstdint></code><br />
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<code>#include <iostream></code><br />
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</div><div class="textblock"><div class="dynheader">
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Include dependency graph for count_of_set_bits.cpp:</div>
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<p><a href="../../da/db8/count__of__set__bits_8cpp_source.html">Go to the source code of this file.</a></p>
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<table class="memberdecls">
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<tr class="heading"><td colspan="2"><h2 id="header-namespaces" class="groupheader"><a id="namespaces" name="namespaces"></a>
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Namespaces</h2></td></tr>
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<tr class="memitem:bit_5Fmanipulation" id="r_bit_5Fmanipulation"><td class="memItemLeft" align="right" valign="top">namespace  </td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d81/namespacebit__manipulation.html">bit_manipulation</a></td></tr>
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<tr class="memdesc:d7/d81/namespacebit__manipulation"><td class="mdescLeft"> </td><td class="mdescRight">for std::string <br /></td></tr>
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<tr class="memitem:count_5Fof_5Fset_5Fbits" id="r_count_5Fof_5Fset_5Fbits"><td class="memItemLeft" align="right" valign="top">namespace  </td><td class="memItemRight" valign="bottom"><a class="el" href="../../dd/dae/namespacecount__of__set__bits.html">count_of_set_bits</a></td></tr>
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<tr class="memdesc:dd/dae/namespacecount__of__set__bits"><td class="mdescLeft"> </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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</table><table class="memberdecls">
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<tr class="heading"><td colspan="2"><h2 id="header-func-members" class="groupheader"><a id="func-members" name="func-members"></a>
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Functions</h2></td></tr>
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<tr class="memitem:aea9e56e21fc34d417d702319303a285a" id="r_aea9e56e21fc34d417d702319303a285a"><td class="memItemLeft" align="right" valign="top">std::uint64_t </td><td class="memItemRight" valign="bottom"><a class="el" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a> (std ::uint64_t n)</td></tr>
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<tr class="memdesc:aea9e56e21fc34d417d702319303a285a"><td class="mdescLeft"> </td><td class="mdescRight">The main function implements set bit count. <br /></td></tr>
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<tr class="memitem:aa8dca7b867074164d5f45b0f3851269d" id="r_aa8dca7b867074164d5f45b0f3851269d"><td class="memItemLeft" align="right" valign="top">static void </td><td class="memItemRight" valign="bottom"><a class="el" href="#aa8dca7b867074164d5f45b0f3851269d">test</a> ()</td></tr>
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<tr class="memitem:ae66f6b31b5ad750f1fe042a706a4e3d4" id="r_ae66f6b31b5ad750f1fe042a706a4e3d4"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="#ae66f6b31b5ad750f1fe042a706a4e3d4">main</a> ()</td></tr>
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<tr class="memdesc:ae66f6b31b5ad750f1fe042a706a4e3d4"><td class="mdescLeft"> </td><td class="mdescRight">Main function. <br /></td></tr>
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</table>
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<a name="details" id="details"></a><h2 id="header-details" class="groupheader">Detailed Description</h2>
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<div class="textblock"><p>Implementation to [count number of set bits of a number] (<a href="https://www.geeksforgeeks.org/count-set-bits-in-an-integer/">https://www.geeksforgeeks.org/count-set-bits-in-an-integer/</a>) in an integer. </p>
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<p>We are given an integer number. We need to calculate the number of set bits in it.</p>
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<p>A binary number consists of two digits. They are 0 & 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>
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<dd>
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<a href="https://github.com/prashant-th18" target="_blank">Prashant Thakur</a> </dd></dl>
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<p class="definition">Definition in file <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html">count_of_set_bits.cpp</a>.</p>
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</div><a name="doc-func-members" id="doc-func-members"></a><h2 id="header-doc-func-members" class="groupheader">Function Documentation</h2>
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<a id="aea9e56e21fc34d417d702319303a285a" name="aea9e56e21fc34d417d702319303a285a"></a>
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<h2 class="memtitle"><span class="permalink"><a href="#aea9e56e21fc34d417d702319303a285a">◆ </a></span>countSetBits()</h2>
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<td class="memname">std::uint64_t bit_manipulation::count_of_set_bits::countSetBits </td>
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<td>(</td>
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<td class="paramtype">std ::uint64_t</td> <td class="paramname"><span class="paramname"><em>n</em></span></td><td>)</td>
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<p>The main function implements set bit count. </p>
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<dl class="params"><dt>Parameters</dt><dd>
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<table class="params">
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<tr><td class="paramname">n</td><td>is the number whose set bit will be counted </td></tr>
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</table>
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</dd>
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</dl>
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<dl class="section return"><dt>Returns</dt><dd>total number of set-bits in the binary representation of number <span class="tt">n</span> </dd></dl>
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<p class="definition">Definition at line <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html#l00038">38</a> of file <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html">count_of_set_bits.cpp</a>.</p>
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<div class="fragment"><div class="line"><span class="lineno"> 39</span> { <span class="comment">// uint64_t is preferred over int so that</span></div>
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<div class="line"><span class="lineno"> 40</span> <span class="comment">// no Overflow can be there.</span></div>
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<div class="line"><span class="lineno"> 41</span> <span class="comment">//It's preferred over int64_t because it Guarantees that inputs are always non-negative, </span></div>
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<div class="line"><span class="lineno"> 42</span> <span class="comment">//which matches the algorithmic problem statement.</span></div>
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<div class="line"><span class="lineno"> 43</span> <span class="comment">//set bit counting is conceptually defined only for non-negative numbers.</span></div>
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<div class="line"><span class="lineno"> 44</span> <span class="comment">//Provides a type Safety: Using an unsigned type helps prevent accidental negative values,</span></div>
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<div class="line"><span class="lineno"> 45</span> </div>
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<div class="line"><span class="lineno"> 46</span> std::uint64_t count = 0; <span class="comment">// "count" variable is used to count number of set-bits('1')</span></div>
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<div class="line"><span class="lineno"> 47</span> <span class="comment">// in binary representation of number 'n'</span></div>
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<div class="line"><span class="lineno"> 48</span> <span class="comment">//Count is uint64_t because it Prevents theoretical overflow if someone passes very large integers.</span></div>
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<div class="line"><span class="lineno"> 49</span> <span class="comment">// Behavior stays the same for all normal inputs.</span></div>
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<div class="line"><span class="lineno"> 50</span> <span class="comment">// Safer for edge cases.</span></div>
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<div class="line"><span class="lineno"> 51</span> </div>
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<div class="line"><span class="lineno"> 52</span> <span class="keywordflow">while</span> (n != 0) {</div>
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<div class="line"><span class="lineno"> 53</span> ++count;</div>
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<div class="line"><span class="lineno"> 54</span> n = (n & (n - 1));</div>
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<div class="line"><span class="lineno"> 55</span> }</div>
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<div class="line"><span class="lineno"> 56</span> <span class="keywordflow">return</span> count;</div>
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<div class="line"><span class="lineno"> 57</span> <span class="comment">// Why this algorithm is better than the standard one?</span></div>
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<div class="line"><span class="lineno"> 58</span> <span class="comment">// Because this algorithm runs the same number of times as the number of</span></div>
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<div class="line"><span class="lineno"> 59</span> <span class="comment">// set-bits in it. Means if my number is having "3" set bits, then this</span></div>
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<div class="line"><span class="lineno"> 60</span> <span class="comment">// while loop will run only "3" times!!</span></div>
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<div class="line"><span class="lineno"> 61</span>}</div>
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<a id="ae66f6b31b5ad750f1fe042a706a4e3d4" name="ae66f6b31b5ad750f1fe042a706a4e3d4"></a>
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<h2 class="memtitle"><span class="permalink"><a href="#ae66f6b31b5ad750f1fe042a706a4e3d4">◆ </a></span>main()</h2>
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<td class="memname">int main </td>
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<td>(</td>
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<td class="paramtype">void</td> <td class="paramname"><span class="paramname"><em></em></span></td><td>)</td>
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<td></td>
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<p>Main function. </p>
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<dl class="section return"><dt>Returns</dt><dd>0 on exit </dd></dl>
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<p class="definition">Definition at line <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html#l00088">88</a> of file <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html">count_of_set_bits.cpp</a>.</p>
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<div class="fragment"><div class="line"><span class="lineno"> 88</span> {</div>
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<div class="line"><span class="lineno"> 89</span> <a class="code hl_function" href="../../dd/d1e/generate__parentheses_8cpp.html#aa8dca7b867074164d5f45b0f3851269d">test</a>(); <span class="comment">// run self-test implementations</span></div>
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<div class="line"><span class="lineno"> 90</span> <span class="keywordflow">return</span> 0;</div>
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<div class="line"><span class="lineno"> 91</span>}</div>
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<div class="ttc" id="agenerate__parentheses_8cpp_html_aa8dca7b867074164d5f45b0f3851269d"><div class="ttname"><a href="../../dd/d1e/generate__parentheses_8cpp.html#aa8dca7b867074164d5f45b0f3851269d">test</a></div><div class="ttdeci">static void test()</div><div class="ttdoc">Self-test implementations.</div><div class="ttdef"><b>Definition</b> <a href="../../dd/d1e/generate__parentheses_8cpp_source.html#l00082">generate_parentheses.cpp:82</a></div></div>
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<a id="aa8dca7b867074164d5f45b0f3851269d" name="aa8dca7b867074164d5f45b0f3851269d"></a>
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<h2 class="memtitle"><span class="permalink"><a href="#aa8dca7b867074164d5f45b0f3851269d">◆ </a></span>test()</h2>
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<td class="memname">void test </td>
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<td>(</td>
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<span class="mlabels"><span class="mlabel static">static</span></span> </td>
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<p class="definition">Definition at line <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html#l00065">65</a> of file <a class="el" href="../../da/db8/count__of__set__bits_8cpp_source.html">count_of_set_bits.cpp</a>.</p>
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<div class="fragment"><div class="line"><span class="lineno"> 65</span> {</div>
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<div class="line"><span class="lineno"> 66</span> <span class="comment">// n = 4 return 1</span></div>
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<div class="line"><span class="lineno"> 67</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(4) == 1);</div>
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<div class="line"><span class="lineno"> 68</span> <span class="comment">// n = 6 return 2</span></div>
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<div class="line"><span class="lineno"> 69</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(6) == 2);</div>
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<div class="line"><span class="lineno"> 70</span> <span class="comment">// n = 13 return 3</span></div>
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<div class="line"><span class="lineno"> 71</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(13) == 3);</div>
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<div class="line"><span class="lineno"> 72</span> <span class="comment">// n = 9 return 2</span></div>
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<div class="line"><span class="lineno"> 73</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(9) == 2);</div>
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<div class="line"><span class="lineno"> 74</span> <span class="comment">// n = 15 return 4</span></div>
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<div class="line"><span class="lineno"> 75</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(15) == 4);</div>
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<div class="line"><span class="lineno"> 76</span> <span class="comment">// n = 25 return 3</span></div>
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<div class="line"><span class="lineno"> 77</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(25) == 3);</div>
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<div class="line"><span class="lineno"> 78</span> <span class="comment">// n = 97 return 3</span></div>
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<div class="line"><span class="lineno"> 79</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(97) == 3);</div>
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<div class="line"><span class="lineno"> 80</span> <span class="comment">// n = 31 return 5</span></div>
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<div class="line"><span class="lineno"> 81</span> assert(<a class="code hl_function" href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a>(31) == 5);</div>
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<div class="line"><span class="lineno"> 82</span> std::cout << <span class="stringliteral">"All test cases successfully passed!"</span> << std::endl;</div>
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<div class="line"><span class="lineno"> 83</span>}</div>
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<div class="ttc" id="acount__of__set__bits_8cpp_html_aea9e56e21fc34d417d702319303a285a"><div class="ttname"><a href="#aea9e56e21fc34d417d702319303a285a">bit_manipulation::count_of_set_bits::countSetBits</a></div><div class="ttdeci">std::uint64_t countSetBits(std ::uint64_t n)</div><div class="ttdoc">The main function implements set bit count.</div><div class="ttdef"><b>Definition</b> <a href="../../da/db8/count__of__set__bits_8cpp_source.html#l00038">count_of_set_bits.cpp:38</a></div></div>
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