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<div class="headertitle"><div class="title">power_of_2.cpp</div></div>
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<a href="../../dc/d6d/power__of__2_8cpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno"> 1</span></div>
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<div class="line"><a id="l00017" name="l00017"></a><span class="lineno"> 17</span> </div>
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<div class="line"><a id="l00018" name="l00018"></a><span class="lineno"> 18</span><span class="preprocessor">#include <cassert></span> </div>
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<div class="line"><a id="l00019" name="l00019"></a><span class="lineno"> 19</span><span class="preprocessor">#include <cstdint></span></div>
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<div class="line"><a id="l00020" name="l00020"></a><span class="lineno"> 20</span><span class="preprocessor">#include <iostream></span> </div>
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<div class="line"><a id="l00021" name="l00021"></a><span class="lineno"> 21</span></div>
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<div class="line"><a id="l00026" name="l00026"></a><span class="lineno"> 26</span><span class="keyword">namespace </span><a class="code hl_namespace" href="../../d7/d81/namespacebit__manipulation.html">bit_manipulation</a> {</div>
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<div class="foldopen" id="foldopen00032" data-start="{" data-end="}">
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<div class="line"><a id="l00032" name="l00032"></a><span class="lineno"><a class="line" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f"> 32</a></span><span class="keywordtype">bool</span> <a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">isPowerOfTwo</a>(std ::int64_t n) { <span class="comment">// int64_t is preferred over int so that</span></div>
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<div class="line"><a id="l00033" name="l00033"></a><span class="lineno"> 33</span> <span class="comment">// no Overflow can be there.</span></div>
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<div class="line"><a id="l00034" name="l00034"></a><span class="lineno"> 34</span> </div>
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<div class="line"><a id="l00035" name="l00035"></a><span class="lineno"> 35</span> <span class="keywordflow">return</span> n > 0 && !(n & n - 1); <span class="comment">// If we subtract a power of 2 numbers by 1</span></div>
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<div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span> <span class="comment">// then all unset bits after the only set bit become set; and the set bit</span></div>
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<div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span> <span class="comment">// becomes unset.</span></div>
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<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span> </div>
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<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span> <span class="comment">// If a number n is a power of 2 then bitwise and of n-1 and n will be zero.</span></div>
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<div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span> <span class="comment">// The expression n&(n-1) will not work when n is 0.</span></div>
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<div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span> <span class="comment">// To handle this case also, our expression will become n& (!n&(n-1))</span></div>
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<div class="line"><a id="l00042" name="l00042"></a><span class="lineno"> 42</span>}</div>
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</div>
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<div class="line"><a id="l00043" name="l00043"></a><span class="lineno"> 43</span>} <span class="comment">// namespace bit_manipulation</span></div>
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<div class="line"><a id="l00044" name="l00044"></a><span class="lineno"> 44</span></div>
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<div class="foldopen" id="foldopen00049" data-start="{" data-end="}">
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<div class="line"><a id="l00049" name="l00049"></a><span class="lineno"><a class="line" href="../../dc/d6d/power__of__2_8cpp.html#aa8dca7b867074164d5f45b0f3851269d"> 49</a></span><span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="../../dc/d6d/power__of__2_8cpp.html#aa8dca7b867074164d5f45b0f3851269d">test</a>() {</div>
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<div class="line"><a id="l00050" name="l00050"></a><span class="lineno"> 50</span> <span class="comment">// n = 4 return true</span></div>
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<div class="line"><a id="l00051" name="l00051"></a><span class="lineno"> 51</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(4) == <span class="keyword">true</span>);</div>
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<div class="line"><a id="l00052" name="l00052"></a><span class="lineno"> 52</span> <span class="comment">// n = 6 return false</span></div>
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<div class="line"><a id="l00053" name="l00053"></a><span class="lineno"> 53</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(6) == <span class="keyword">false</span>);</div>
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<div class="line"><a id="l00054" name="l00054"></a><span class="lineno"> 54</span> <span class="comment">// n = 13 return false</span></div>
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<div class="line"><a id="l00055" name="l00055"></a><span class="lineno"> 55</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(13) == <span class="keyword">false</span>);</div>
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<div class="line"><a id="l00056" name="l00056"></a><span class="lineno"> 56</span> <span class="comment">// n = 64 return true</span></div>
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<div class="line"><a id="l00057" name="l00057"></a><span class="lineno"> 57</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(64) == <span class="keyword">true</span>);</div>
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<div class="line"><a id="l00058" name="l00058"></a><span class="lineno"> 58</span> <span class="comment">// n = 15 return false</span></div>
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<div class="line"><a id="l00059" name="l00059"></a><span class="lineno"> 59</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(15) == <span class="keyword">false</span>);</div>
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<div class="line"><a id="l00060" name="l00060"></a><span class="lineno"> 60</span> <span class="comment">// n = 32 return true</span></div>
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<div class="line"><a id="l00061" name="l00061"></a><span class="lineno"> 61</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(32) == <span class="keyword">true</span>);</div>
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<div class="line"><a id="l00062" name="l00062"></a><span class="lineno"> 62</span> <span class="comment">// n = 97 return false</span></div>
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<div class="line"><a id="l00063" name="l00063"></a><span class="lineno"> 63</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(97) == <span class="keyword">false</span>);</div>
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<div class="line"><a id="l00064" name="l00064"></a><span class="lineno"> 64</span> <span class="comment">// n = 1024 return true</span></div>
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<div class="line"><a id="l00065" name="l00065"></a><span class="lineno"> 65</span> assert(<a class="code hl_function" href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a>(1024) == <span class="keyword">true</span>);</div>
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<div class="line"><a id="l00066" name="l00066"></a><span class="lineno"> 66</span> std::cout << <span class="stringliteral">"All test cases successfully passed!"</span> << std::endl;</div>
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<div class="line"><a id="l00067" name="l00067"></a><span class="lineno"> 67</span>}</div>
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</div>
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<div class="line"><a id="l00068" name="l00068"></a><span class="lineno"> 68</span></div>
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<div class="foldopen" id="foldopen00072" data-start="{" data-end="}">
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<div class="line"><a id="l00072" name="l00072"></a><span class="lineno"><a class="line" href="../../dc/d6d/power__of__2_8cpp.html#ae66f6b31b5ad750f1fe042a706a4e3d4"> 72</a></span><span class="keywordtype">int</span> <a class="code hl_function" href="../../dc/d6d/power__of__2_8cpp.html#ae66f6b31b5ad750f1fe042a706a4e3d4">main</a>() {</div>
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<div class="line"><a id="l00073" name="l00073"></a><span class="lineno"> 73</span> <a class="code hl_function" href="../../dc/d6d/power__of__2_8cpp.html#aa8dca7b867074164d5f45b0f3851269d">test</a>(); <span class="comment">// run self-test implementations</span></div>
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<div class="line"><a id="l00074" name="l00074"></a><span class="lineno"> 74</span> <span class="keywordflow">return</span> 0;</div>
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<div class="line"><a id="l00075" name="l00075"></a><span class="lineno"> 75</span>}</div>
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</div>
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<div class="ttc" id="anamespacebit__manipulation_html"><div class="ttname"><a href="../../d7/d81/namespacebit__manipulation.html">bit_manipulation</a></div><div class="ttdoc">for std::string</div></div>
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<div class="ttc" id="anamespacebit__manipulation_html_a5032470c9974bbd6ec254bf296530a5f"><div class="ttname"><a href="../../d7/d81/namespacebit__manipulation.html#a5032470c9974bbd6ec254bf296530a5f">bit_manipulation::isPowerOfTwo</a></div><div class="ttdeci">bool isPowerOfTwo(std ::int64_t n)</div><div class="ttdoc">The main function implements check for power of 2.</div><div class="ttdef"><b>Definition</b> <a href="#l00032">power_of_2.cpp:32</a></div></div>
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<div class="ttc" id="apower__of__2_8cpp_html_aa8dca7b867074164d5f45b0f3851269d"><div class="ttname"><a href="../../dc/d6d/power__of__2_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="#l00049">power_of_2.cpp:49</a></div></div>
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<div class="ttc" id="apower__of__2_8cpp_html_ae66f6b31b5ad750f1fe042a706a4e3d4"><div class="ttname"><a href="../../dc/d6d/power__of__2_8cpp.html#ae66f6b31b5ad750f1fe042a706a4e3d4">main</a></div><div class="ttdeci">int main()</div><div class="ttdoc">Main function.</div><div class="ttdef"><b>Definition</b> <a href="#l00072">power_of_2.cpp:72</a></div></div>
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