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<p>Implementation of <a href="https://en.wikipedia.org/wiki/Cycle_detection" target="_blank">Floyd's Cycle Detection</a> algorithm.
<a href="#details">More...</a></p>
<div class="textblock"><code>#include &lt;cassert&gt;</code><br />
<code>#include &lt;cstdint&gt;</code><br />
<code>#include &lt;iostream&gt;</code><br />
<code>#include &lt;vector&gt;</code><br />
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Include dependency graph for floyd_cycle_detection_algo.cpp:</div>
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<p><a href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html">Go to the source code of this file.</a></p>
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Namespaces</h2></td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">namespace &#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d9/dca/namespacesearch.html">search</a></td></tr>
<tr class="memdesc:d9/dca/namespacesearch"><td class="mdescLeft">&#160;</td><td class="mdescRight">for std::assert <br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">namespace &#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../da/d82/namespacecycle__detection.html">cycle_detection</a></td></tr>
<tr class="memdesc:da/d82/namespacecycle__detection"><td class="mdescLeft">&#160;</td><td class="mdescRight">Functions for the <a href="https://en.wikipedia.org/wiki/Cycle_detection" target="_blank">Floyd's Cycle Detection</a> algorithm. <br /></td></tr>
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Functions</h2></td></tr>
<tr class="memitem:a81ffc7a2c6bf530c8a496864e7a3ad88" id="r_a81ffc7a2c6bf530c8a496864e7a3ad88"><td class="memTemplParams" colspan="2">template&lt;typename T&gt; </td></tr>
<tr class="memitem:a81ffc7a2c6bf530c8a496864e7a3ad88"><td class="memTemplItemLeft" align="right" valign="top">int32_t&#160;</td><td class="memTemplItemRight" valign="bottom"><a class="el" href="#a81ffc7a2c6bf530c8a496864e7a3ad88">search::cycle_detection::duplicateNumber</a> (const std::vector&lt; T &gt; &amp;in_arr, const uint32_t &amp;n)</td></tr>
<tr class="memdesc:a81ffc7a2c6bf530c8a496864e7a3ad88"><td class="mdescLeft">&#160;</td><td class="mdescRight">The main function implements search algorithm. <br /></td></tr>
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<tr class="memitem:aa8dca7b867074164d5f45b0f3851269d" id="r_aa8dca7b867074164d5f45b0f3851269d"><td class="memItemLeft" align="right" valign="top">static void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#aa8dca7b867074164d5f45b0f3851269d">test</a> ()</td></tr>
<tr class="memdesc:aa8dca7b867074164d5f45b0f3851269d"><td class="mdescLeft">&#160;</td><td class="mdescRight">Self-test implementations. <br /></td></tr>
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<tr class="memitem:ae66f6b31b5ad750f1fe042a706a4e3d4" id="r_ae66f6b31b5ad750f1fe042a706a4e3d4"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#ae66f6b31b5ad750f1fe042a706a4e3d4">main</a> ()</td></tr>
<tr class="memdesc:ae66f6b31b5ad750f1fe042a706a4e3d4"><td class="mdescLeft">&#160;</td><td class="mdescRight">Main function. <br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Implementation of <a href="https://en.wikipedia.org/wiki/Cycle_detection" target="_blank">Floyd's Cycle Detection</a> algorithm. </p>
<p>Given an array of integers containing 'n + 1' integers, where each integer is in the range [1, n] inclusive. If there is only one duplicate number in the input array, this algorithm returns the duplicate number in O(1) space and the time complexity is less than O(n^2) without modifying the original array, otherwise, it returns -1. </p><dl class="section author"><dt>Author</dt><dd><a href="https://github.com/Swastyy" target="_blank">Swastika Gupta</a> </dd></dl>
<p class="definition">Definition in file <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html">floyd_cycle_detection_algo.cpp</a>.</p>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="a81ffc7a2c6bf530c8a496864e7a3ad88" name="a81ffc7a2c6bf530c8a496864e7a3ad88"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a81ffc7a2c6bf530c8a496864e7a3ad88">&#9670;&#160;</a></span>duplicateNumber()</h2>
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template&lt;typename T&gt; </div>
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<td class="memname">int32_t search::cycle_detection::duplicateNumber </td>
<td>(</td>
<td class="paramtype">const std::vector&lt; T &gt; &amp;</td> <td class="paramname"><span class="paramname"><em>in_arr</em></span>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const uint32_t &amp;</td> <td class="paramname"><span class="paramname"><em>n</em></span>&#160;)</td>
</tr>
</table>
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<p>The main function implements search algorithm. </p>
<dl class="tparams"><dt>Template Parameters</dt><dd>
<table class="tparams">
<tr><td class="paramname">T</td><td>type of array </td></tr>
</table>
</dd>
</dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">in_arr</td><td>the input array </td></tr>
<tr><td class="paramname">n</td><td>size of array </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>the duplicate number </dd></dl>
<p class="definition">Definition at line <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html#l00037">37</a> of file <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html">floyd_cycle_detection_algo.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 37</span> {</div>
<div class="line"><span class="lineno"> 38</span> <span class="keywordflow">if</span> (n == 0 ||</div>
<div class="line"><span class="lineno"> 39</span> n == 1) { <span class="comment">// to find duplicate in an array its size should be atleast 2</span></div>
<div class="line"><span class="lineno"> 40</span> <span class="keywordflow">return</span> -1;</div>
<div class="line"><span class="lineno"> 41</span> }</div>
<div class="line"><span class="lineno"> 42</span> uint32_t tortoise = in_arr[0]; <span class="comment">// variable tortoise is used for the longer</span></div>
<div class="line"><span class="lineno"> 43</span> <span class="comment">// jumps in the array</span></div>
<div class="line"><span class="lineno"> 44</span> uint32_t hare =</div>
<div class="line"><span class="lineno"> 45</span> in_arr[0]; <span class="comment">// variable hare is used for shorter jumps in the array</span></div>
<div class="line"><span class="lineno"> 46</span> <span class="keywordflow">do</span> {</div>
<div class="line"><span class="lineno"> 47</span> tortoise = in_arr[tortoise];</div>
<div class="line"><span class="lineno"> 48</span> hare = in_arr[in_arr[hare]];</div>
<div class="line"><span class="lineno"> 49</span> } <span class="keywordflow">while</span> (tortoise != hare);</div>
<div class="line"><span class="lineno"> 50</span> tortoise = in_arr[0];</div>
<div class="line"><span class="lineno"> 51</span> <span class="keywordflow">while</span> (tortoise != hare) {</div>
<div class="line"><span class="lineno"> 52</span> tortoise = in_arr[tortoise];</div>
<div class="line"><span class="lineno"> 53</span> hare = in_arr[hare];</div>
<div class="line"><span class="lineno"> 54</span> }</div>
<div class="line"><span class="lineno"> 55</span> <span class="keywordflow">return</span> tortoise;</div>
<div class="line"><span class="lineno"> 56</span>}</div>
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<a id="ae66f6b31b5ad750f1fe042a706a4e3d4" name="ae66f6b31b5ad750f1fe042a706a4e3d4"></a>
<h2 class="memtitle"><span class="permalink"><a href="#ae66f6b31b5ad750f1fe042a706a4e3d4">&#9670;&#160;</a></span>main()</h2>
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<td class="memname">int main </td>
<td>(</td>
<td class="paramtype">void</td> <td class="paramname"><span class="paramname"><em></em></span></td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<p>Main function. </p>
<dl class="section return"><dt>Returns</dt><dd>0 on exit </dd></dl>
<p class="definition">Definition at line <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html#l00095">95</a> of file <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html">floyd_cycle_detection_algo.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 95</span> {</div>
<div class="line"><span class="lineno"> 96</span> <a class="code hl_function" href="#aa8dca7b867074164d5f45b0f3851269d">test</a>(); <span class="comment">// run self-test implementations</span></div>
<div class="line"><span class="lineno"> 97</span> <span class="keywordflow">return</span> 0;</div>
<div class="line"><span class="lineno"> 98</span>}</div>
<div class="ttc" id="afloyd__cycle__detection__algo_8cpp_html_aa8dca7b867074164d5f45b0f3851269d"><div class="ttname"><a href="#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="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html#l00064">floyd_cycle_detection_algo.cpp:64</a></div></div>
</div><!-- fragment -->
</div>
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<a id="aa8dca7b867074164d5f45b0f3851269d" name="aa8dca7b867074164d5f45b0f3851269d"></a>
<h2 class="memtitle"><span class="permalink"><a href="#aa8dca7b867074164d5f45b0f3851269d">&#9670;&#160;</a></span>test()</h2>
<div class="memitem">
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<td class="mlabels-left">
<table class="memname">
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<td class="memname">static void test </td>
<td>(</td>
<td class="paramname"><span class="paramname"><em></em></span></td><td>)</td>
<td></td>
</tr>
</table>
</td>
<td class="mlabels-right">
<span class="mlabels"><span class="mlabel static">static</span></span> </td>
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<p>Self-test implementations. </p>
<dl class="section return"><dt>Returns</dt><dd>void </dd></dl>
<p class="definition">Definition at line <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html#l00064">64</a> of file <a class="el" href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html">floyd_cycle_detection_algo.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 64</span> {</div>
<div class="line"><span class="lineno"> 65</span> <span class="comment">// 1st test</span></div>
<div class="line"><span class="lineno"> 66</span> <span class="comment">// [3, 4, 8, 5, 9, 1, 2, 6, 7, 4] return 4</span></div>
<div class="line"><span class="lineno"> 67</span> std::vector&lt;uint32_t&gt; array1 = {3, 4, 8, 5, 9, 1, 2, 6, 7, 4};</div>
<div class="line"><span class="lineno"> 68</span> std::cout &lt;&lt; <span class="stringliteral">&quot;Test 1... &quot;</span>;</div>
<div class="line"><span class="lineno"> 69</span> assert(<a class="code hl_function" href="#a81ffc7a2c6bf530c8a496864e7a3ad88">search::cycle_detection::duplicateNumber</a>(array1, array1.size()) ==</div>
<div class="line"><span class="lineno"> 70</span> 4); <span class="comment">// here the duplicate number is 4</span></div>
<div class="line"><span class="lineno"> 71</span> std::cout &lt;&lt; <span class="stringliteral">&quot;passed&quot;</span> &lt;&lt; std::endl;</div>
<div class="line"><span class="lineno"> 72</span> </div>
<div class="line"><span class="lineno"> 73</span> <span class="comment">// 2nd test</span></div>
<div class="line"><span class="lineno"> 74</span> <span class="comment">// [1, 2, 3, 4, 2] return 2</span></div>
<div class="line"><span class="lineno"> 75</span> std::vector&lt;uint32_t&gt; array2 = {1, 2, 3, 4, 2};</div>
<div class="line"><span class="lineno"> 76</span> std::cout &lt;&lt; <span class="stringliteral">&quot;Test 2... &quot;</span>;</div>
<div class="line"><span class="lineno"> 77</span> assert(<a class="code hl_function" href="#a81ffc7a2c6bf530c8a496864e7a3ad88">search::cycle_detection::duplicateNumber</a>(array2, array2.size()) ==</div>
<div class="line"><span class="lineno"> 78</span> 2); <span class="comment">// here the duplicate number is 2</span></div>
<div class="line"><span class="lineno"> 79</span> std::cout &lt;&lt; <span class="stringliteral">&quot;passed&quot;</span> &lt;&lt; std::endl;</div>
<div class="line"><span class="lineno"> 80</span> </div>
<div class="line"><span class="lineno"> 81</span> <span class="comment">// 3rd test</span></div>
<div class="line"><span class="lineno"> 82</span> <span class="comment">// [] return -1</span></div>
<div class="line"><span class="lineno"> 83</span> std::vector&lt;uint32_t&gt; array3 = {};</div>
<div class="line"><span class="lineno"> 84</span> std::cout &lt;&lt; <span class="stringliteral">&quot;Test 3... &quot;</span>;</div>
<div class="line"><span class="lineno"> 85</span> assert(<a class="code hl_function" href="#a81ffc7a2c6bf530c8a496864e7a3ad88">search::cycle_detection::duplicateNumber</a>(array3, array3.size()) ==</div>
<div class="line"><span class="lineno"> 86</span> -1); <span class="comment">// since the input array is empty no duplicate number exists in</span></div>
<div class="line"><span class="lineno"> 87</span> <span class="comment">// this case</span></div>
<div class="line"><span class="lineno"> 88</span> std::cout &lt;&lt; <span class="stringliteral">&quot;passed&quot;</span> &lt;&lt; std::endl;</div>
<div class="line"><span class="lineno"> 89</span>}</div>
<div class="ttc" id="afloyd__cycle__detection__algo_8cpp_html_a81ffc7a2c6bf530c8a496864e7a3ad88"><div class="ttname"><a href="#a81ffc7a2c6bf530c8a496864e7a3ad88">search::cycle_detection::duplicateNumber</a></div><div class="ttdeci">int32_t duplicateNumber(const std::vector&lt; T &gt; &amp;in_arr, const uint32_t &amp;n)</div><div class="ttdoc">The main function implements search algorithm.</div><div class="ttdef"><b>Definition</b> <a href="../../db/dc4/floyd__cycle__detection__algo_8cpp_source.html#l00037">floyd_cycle_detection_algo.cpp:37</a></div></div>
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