TheAlgorithms-C/d7/d91/problem__15_2sol1_8c.html
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<div id="projectbrief">Set of algorithms implemented in C.</div>
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<a href="#func-members">Functions</a> </div>
<div class="headertitle"><div class="title">sol1.c File Reference</div></div>
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<p><a href="https://projecteuler.net/problem=15" target="_blank">Problem 15</a> solution
<a href="#details">More...</a></p>
<div class="textblock"><code>#include &lt;stdint.h&gt;</code><br />
<code>#include &lt;stdio.h&gt;</code><br />
<code>#include &lt;stdlib.h&gt;</code><br />
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Include dependency graph for sol1.c:</div>
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Functions</h2></td></tr>
<tr class="memitem:a4650d1d3897633d84253f93433f601d6"><td class="memItemLeft" align="right" valign="top">unsigned long long&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d91/problem__15_2sol1_8c.html#a4650d1d3897633d84253f93433f601d6">number_of_paths</a> (int N)</td></tr>
<tr class="memdesc:a4650d1d3897633d84253f93433f601d6"><td class="mdescLeft">&#160;</td><td class="mdescRight">At every node, there are 2 possible ways to move -&gt; down or right. <a href="../../d7/d91/problem__15_2sol1_8c.html#a4650d1d3897633d84253f93433f601d6">More...</a><br /></td></tr>
<tr class="separator:a4650d1d3897633d84253f93433f601d6"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:a3c04138a5bfe5d72780bb7e82a18e627"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d91/problem__15_2sol1_8c.html#a3c04138a5bfe5d72780bb7e82a18e627">main</a> (int argc, char **argv)</td></tr>
<tr class="memdesc:a3c04138a5bfe5d72780bb7e82a18e627"><td class="mdescLeft">&#160;</td><td class="mdescRight">Main function. <a href="../../d7/d91/problem__15_2sol1_8c.html#a3c04138a5bfe5d72780bb7e82a18e627">More...</a><br /></td></tr>
<tr class="separator:a3c04138a5bfe5d72780bb7e82a18e627"><td class="memSeparator" colspan="2">&#160;</td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p ><a href="https://projecteuler.net/problem=15" target="_blank">Problem 15</a> solution </p>
<dl class="section author"><dt>Author</dt><dd><a href="https://github.com/kvedala" target="_blank">Krishna Vedala</a> </dd></dl>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="a3c04138a5bfe5d72780bb7e82a18e627" name="a3c04138a5bfe5d72780bb7e82a18e627"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a3c04138a5bfe5d72780bb7e82a18e627">&#9670;&nbsp;</a></span>main()</h2>
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<td class="memname">int main </td>
<td>(</td>
<td class="paramtype">int&#160;</td>
<td class="paramname"><em>argc</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype">char **&#160;</td>
<td class="paramname"><em>argv</em>&#160;</td>
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<td>)</td>
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<p>Main function. </p>
<div class="fragment"><div class="line"><a id="l00031" name="l00031"></a><span class="lineno"> 31</span>{</div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno"> 32</span> <span class="keywordtype">int</span> N = 20;</div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno"> 33</span> </div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno"> 34</span> <span class="keywordflow">if</span> (argc == 2)</div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno"> 35</span> N = atoi(argv[1]);</div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span> </div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span> printf(<span class="stringliteral">&quot;Number of ways to traverse diagonal of %dx%d grid = %llu\n&quot;</span>, N, N,</div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span> <a class="code hl_function" href="../../d7/d91/problem__15_2sol1_8c.html#a4650d1d3897633d84253f93433f601d6">number_of_paths</a>(N));</div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span> </div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span> <span class="keywordflow">return</span> 0;</div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span>}</div>
<div class="ttc" id="aproblem__15_2sol1_8c_html_a4650d1d3897633d84253f93433f601d6"><div class="ttname"><a href="../../d7/d91/problem__15_2sol1_8c.html#a4650d1d3897633d84253f93433f601d6">number_of_paths</a></div><div class="ttdeci">unsigned long long number_of_paths(int N)</div><div class="ttdoc">At every node, there are 2 possible ways to move -&gt; down or right.</div><div class="ttdef"><b>Definition:</b> sol1.c:17</div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#a4650d1d3897633d84253f93433f601d6">&#9670;&nbsp;</a></span>number_of_paths()</h2>
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<td class="memname">unsigned long long number_of_paths </td>
<td>(</td>
<td class="paramtype">int&#160;</td>
<td class="paramname"><em>N</em></td><td>)</td>
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<p>At every node, there are 2 possible ways to move -&gt; down or right. </p>
<p >Since it is a square grid, there are in all, 2N steps with N down and N right options, without preference for order. Hence, the path can be be traced in N out of 2N number of ways. This is the same as binomial coeeficient. </p>
<div class="fragment"><div class="line"><a id="l00018" name="l00018"></a><span class="lineno"> 18</span>{</div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno"> 19</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> path = 1;</div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno"> 20</span> <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i &lt; N; i++)</div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno"> 21</span> {</div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno"> 22</span> path *= (N &lt;&lt; 1) - i;</div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno"> 23</span> path /= i + 1;</div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno"> 24</span> }</div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno"> 25</span> </div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno"> 26</span> <span class="keywordflow">return</span> path;</div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno"> 27</span>}</div>
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