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<p>Compute double factorial: \(n!!\).
<a href="#details">More...</a></p>
<div class="textblock"><code>#include &lt;cassert&gt;</code><br />
<code>#include &lt;iostream&gt;</code><br />
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Include dependency graph for double_factorial.cpp:</div>
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Functions</h2></td></tr>
<tr class="memitem:a0a3c417360400093891a9ccddaa4be26"><td class="memItemLeft" align="right" valign="top">uint64_t&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d89/double__factorial_8cpp.html#a0a3c417360400093891a9ccddaa4be26">double_factorial_iterative</a> (uint64_t n)</td></tr>
<tr class="separator:a0a3c417360400093891a9ccddaa4be26"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:a68ba20fed2ce427f6469c7689437829d"><td class="memItemLeft" align="right" valign="top">uint64_t&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d89/double__factorial_8cpp.html#a68ba20fed2ce427f6469c7689437829d">double_factorial_recursive</a> (uint64_t n)</td></tr>
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int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="../../d7/d89/double__factorial_8cpp.html#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>Compute double factorial: \(n!!\). </p>
<p>Double factorial of a non-negative integer n, is defined as the product of all the integers from 1 to n that have the same parity (odd or even) as n. <br />
It is also called as semifactorial of a number and is denoted by \(n!!\) </p>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="a0a3c417360400093891a9ccddaa4be26"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a0a3c417360400093891a9ccddaa4be26">&#9670;&nbsp;</a></span>double_factorial_iterative()</h2>
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<td class="memname">uint64_t double_factorial_iterative </td>
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<td class="paramtype">uint64_t&#160;</td>
<td class="paramname"><em>n</em></td><td>)</td>
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<p>Compute double factorial using iterative method </p>
<div class="fragment"><div class="line"><a name="l00016"></a><span class="lineno"> 16</span>&#160; {</div>
<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>&#160; uint64_t res = 1;</div>
<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>&#160; <span class="keywordflow">for</span> (uint64_t i = n;; i -= 2) {</div>
<div class="line"><a name="l00019"></a><span class="lineno"> 19</span>&#160; <span class="keywordflow">if</span> (i == 0 || i == 1)</div>
<div class="line"><a name="l00020"></a><span class="lineno"> 20</span>&#160; <span class="keywordflow">return</span> res;</div>
<div class="line"><a name="l00021"></a><span class="lineno"> 21</span>&#160; res *= i;</div>
<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>&#160; }</div>
<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>&#160; <span class="keywordflow">return</span> res;</div>
<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>&#160;}</div>
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<h2 class="memtitle"><span class="permalink"><a href="#a68ba20fed2ce427f6469c7689437829d">&#9670;&nbsp;</a></span>double_factorial_recursive()</h2>
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<td class="memname">uint64_t double_factorial_recursive </td>
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<td class="paramname"><em>n</em></td><td>)</td>
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<p>Compute double factorial using resursive method. <br />
Recursion can be costly for large numbers. </p>
<div class="fragment"><div class="line"><a name="l00029"></a><span class="lineno"> 29</span>&#160; {</div>
<div class="line"><a name="l00030"></a><span class="lineno"> 30</span>&#160; <span class="keywordflow">if</span> (n &lt;= 1)</div>
<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>&#160; <span class="keywordflow">return</span> 1;</div>
<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>&#160; <span class="keywordflow">return</span> n * <a class="code" href="../../d7/d89/double__factorial_8cpp.html#a68ba20fed2ce427f6469c7689437829d">double_factorial_recursive</a>(n - 2);</div>
<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>&#160;}</div>
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<div class="ttc" id="adouble__factorial_8cpp_html_a68ba20fed2ce427f6469c7689437829d"><div class="ttname"><a href="../../d7/d89/double__factorial_8cpp.html#a68ba20fed2ce427f6469c7689437829d">double_factorial_recursive</a></div><div class="ttdeci">uint64_t double_factorial_recursive(uint64_t n)</div><div class="ttdef"><b>Definition:</b> double_factorial.cpp:29</div></div>
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