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<div id="projectbrief">Set of algorithms implemented in C.</div>
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<a href="#func-members">Functions</a> &#124;
<a href="#var-members">Variables</a> </div>
<div class="headertitle"><div class="title">sol2.c File Reference</div></div>
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<p><a href="https://projecteuler.net/problem=5" target="_blank">Problem 5</a> solution - Naive algorithm (Improved over <a class="el" href="../../dc/d32/problem__5_2sol1_8c.html" title="Problem 5 solution - Naive algorithm (slowest)">problem_5/sol1.c</a>)
<a href="#details">More...</a></p>
<div class="textblock"><code>#include &lt;stdio.h&gt;</code><br />
<code>#include &lt;stdlib.h&gt;</code><br />
</div><div class="textblock"><div class="dynheader">
Include dependency graph for sol2.c:</div>
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Functions</h2></td></tr>
<tr class="memitem:aa7cfa5a28d00d93ec48fab9c3fd5812f"><td class="memItemLeft" align="right" valign="top">static int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d5/d3d/problem__5_2sol2_8c.html#aa7cfa5a28d00d93ec48fab9c3fd5812f">check_number</a> (unsigned long long n)</td></tr>
<tr class="memdesc:aa7cfa5a28d00d93ec48fab9c3fd5812f"><td class="mdescLeft">&#160;</td><td class="mdescRight">Checks if a given number is devisable by every number between 1 and 20. <br /></td></tr>
<tr class="separator:aa7cfa5a28d00d93ec48fab9c3fd5812f"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:a840291bc02cba5474a4cb46a9b9566fe"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d5/d3d/problem__5_2sol2_8c.html#a840291bc02cba5474a4cb46a9b9566fe">main</a> (void)</td></tr>
<tr class="memdesc:a840291bc02cba5474a4cb46a9b9566fe"><td class="mdescLeft">&#160;</td><td class="mdescRight">Main function. <br /></td></tr>
<tr class="separator:a840291bc02cba5474a4cb46a9b9566fe"><td class="memSeparator" colspan="2">&#160;</td></tr>
</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a id="var-members" name="var-members"></a>
Variables</h2></td></tr>
<tr class="memitem:adb59595677da81f071c34f3847fdbaa6"><td class="memItemLeft" align="right" valign="top">static unsigned int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d5/d3d/problem__5_2sol2_8c.html#adb59595677da81f071c34f3847fdbaa6">divisors</a> []</td></tr>
<tr class="memdesc:adb59595677da81f071c34f3847fdbaa6"><td class="mdescLeft">&#160;</td><td class="mdescRight">Hack to store divisors between 1 &amp; 20. <br /></td></tr>
<tr class="separator:adb59595677da81f071c34f3847fdbaa6"><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=5" target="_blank">Problem 5</a> solution - Naive algorithm (Improved over <a class="el" href="../../dc/d32/problem__5_2sol1_8c.html" title="Problem 5 solution - Naive algorithm (slowest)">problem_5/sol1.c</a>) </p>
<p>Little bit improved version of the naive <code><a class="el" href="../../dc/d32/problem__5_2sol1_8c.html" title="Problem 5 solution - Naive algorithm (slowest)">problem_5/sol1.c</a></code>. Since the number has to be divisable by 20, we can start at 20 and go in 20 steps. Also we don't have to check against any number, since most of them are implied by other divisions (i.e. if a number is divisable by 20, it's also divisable by 2, 5, and 10). This all gives a 97% perfomance increase on my machine (9.562 vs 0.257)</p>
<dl class="section see"><dt>See also</dt><dd>Slower: <a class="el" href="../../dc/d32/problem__5_2sol1_8c.html" title="Problem 5 solution - Naive algorithm (slowest)">problem_5/sol1.c</a> </dd>
<dd>
Faster: <a class="el" href="../../d5/d7c/problem__5_2sol3_8c.html" title="Problem 5 solution (Fastest).">problem_5/sol3.c</a> </dd></dl>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="aa7cfa5a28d00d93ec48fab9c3fd5812f" name="aa7cfa5a28d00d93ec48fab9c3fd5812f"></a>
<h2 class="memtitle"><span class="permalink"><a href="#aa7cfa5a28d00d93ec48fab9c3fd5812f">&#9670;&#160;</a></span>check_number()</h2>
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<td class="memname">static int check_number </td>
<td>(</td>
<td class="paramtype">unsigned long long&#160;</td>
<td class="paramname"><em>n</em></td><td>)</td>
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<p>Checks if a given number is devisable by every number between 1 and 20. </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">n</td><td>number to check </td></tr>
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</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if not divisible </dd>
<dd>
1 if divisible </dd></dl>
<div class="fragment"><div class="line"><span class="lineno"> 31</span>{</div>
<div class="line"><span class="lineno"> 32</span> <span class="keywordflow">for</span> (<span class="keywordtype">size_t</span> i = 0; i &lt; 7; ++i)</div>
<div class="line"><span class="lineno"> 33</span> {</div>
<div class="line"><span class="lineno"> 34</span> <span class="keywordflow">if</span> (n % <a class="code hl_variable" href="../../d5/d3d/problem__5_2sol2_8c.html#adb59595677da81f071c34f3847fdbaa6">divisors</a>[i] != 0)</div>
<div class="line"><span class="lineno"> 35</span> {</div>
<div class="line"><span class="lineno"> 36</span> <span class="keywordflow">return</span> 0;</div>
<div class="line"><span class="lineno"> 37</span> }</div>
<div class="line"><span class="lineno"> 38</span> }</div>
<div class="line"><span class="lineno"> 39</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="ttc" id="aproblem__5_2sol2_8c_html_adb59595677da81f071c34f3847fdbaa6"><div class="ttname"><a href="../../d5/d3d/problem__5_2sol2_8c.html#adb59595677da81f071c34f3847fdbaa6">divisors</a></div><div class="ttdeci">static unsigned int divisors[]</div><div class="ttdoc">Hack to store divisors between 1 &amp; 20.</div><div class="ttdef"><b>Definition:</b> sol2.c:21</div></div>
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<a id="a840291bc02cba5474a4cb46a9b9566fe" name="a840291bc02cba5474a4cb46a9b9566fe"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a840291bc02cba5474a4cb46a9b9566fe">&#9670;&#160;</a></span>main()</h2>
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<td class="memname">int main </td>
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<td class="paramtype">void&#160;</td>
<td class="paramname"></td><td>)</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"><span class="lineno"> 49</span>{</div>
<div class="line"><span class="lineno"> 50</span> <span class="keywordflow">for</span> (<span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> <span class="keywordtype">long</span> n = 20;; n += 20)</div>
<div class="line"><span class="lineno"> 51</span> {</div>
<div class="line"><span class="lineno"> 52</span> <span class="keywordflow">if</span> (<a class="code hl_function" href="../../d5/d3d/problem__5_2sol2_8c.html#aa7cfa5a28d00d93ec48fab9c3fd5812f">check_number</a>(n))</div>
<div class="line"><span class="lineno"> 53</span> {</div>
<div class="line"><span class="lineno"> 54</span> printf(<span class="stringliteral">&quot;Result: %llu\n&quot;</span>, n);</div>
<div class="line"><span class="lineno"> 55</span> <span class="keywordflow">break</span>;</div>
<div class="line"><span class="lineno"> 56</span> }</div>
<div class="line"><span class="lineno"> 57</span> }</div>
<div class="line"><span class="lineno"> 58</span> <span class="keywordflow">return</span> 0;</div>
<div class="line"><span class="lineno"> 59</span>}</div>
<div class="ttc" id="aproblem__5_2sol2_8c_html_aa7cfa5a28d00d93ec48fab9c3fd5812f"><div class="ttname"><a href="../../d5/d3d/problem__5_2sol2_8c.html#aa7cfa5a28d00d93ec48fab9c3fd5812f">check_number</a></div><div class="ttdeci">static int check_number(unsigned long long n)</div><div class="ttdoc">Checks if a given number is devisable by every number between 1 and 20.</div><div class="ttdef"><b>Definition:</b> sol2.c:30</div></div>
</div><!-- fragment --><div class="dynheader">
Here is the call graph for this function:</div>
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<h2 class="groupheader">Variable Documentation</h2>
<a id="adb59595677da81f071c34f3847fdbaa6" name="adb59595677da81f071c34f3847fdbaa6"></a>
<h2 class="memtitle"><span class="permalink"><a href="#adb59595677da81f071c34f3847fdbaa6">&#9670;&#160;</a></span>divisors</h2>
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<td class="memname">unsigned int divisors[]</td>
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<span class="mlabels"><span class="mlabel">static</span></span> </td>
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<b>Initial value:</b><div class="fragment"><div class="line">= {</div>
<div class="line"> 11, 13, 14, 16, 17, 18, 19, 20,</div>
<div class="line">}</div>
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<p>Hack to store divisors between 1 &amp; 20. </p>
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