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random_shuffle [C++ Reference]
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<h2><a name="random_shuffle" id="random_shuffle">random_shuffle</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <algorithm></span>
<span class="kw4">void</span> random_shuffle<span class="br0">(</span> random_access_iterator start<span class="sy0">,</span> random_access_iterator end <span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">void</span> random_shuffle<span class="br0">(</span> random_access_iterator start<span class="sy0">,</span> random_access_iterator end<span class="sy0">,</span> RandomNumberGenerator<span class="sy0">&</span> rnd <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The random_shuffle() function randomly re-orders the elements in the range
[start,end). If a random number generator function object rnd is supplied, it
will be used instead of an internal random number generator.
</p>
<p>
The “internal” random number generator is not necessarily the one which can be accessed with rand() and seeded with srand(); this is implementation defined. The SGI STL implementation, for example, uses a different generator.
</p>
<p>
Example
</p>
<pre class="c code c++" style="font-family:monospace;"><span class="co1">// random_shuffle example</span>
<span class="co2">#include <iostream></span>
<span class="co2">#include <algorithm></span>
<span class="co2">#include <functional></span>
<span class="co2">#include <vector></span>
<span class="co2">#include <ctime></span>
<span class="co2">#include <cstdlib></span>
using namespace std<span class="sy0">;</span>
<span class="co1">// random generator function:</span>
ptrdiff_t myrandom <span class="br0">(</span>ptrdiff_t i<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> rand<span class="br0">(</span><span class="br0">)</span><span class="sy0">%</span>i<span class="sy0">;</span><span class="br0">}</span>
<span class="co1">// pointer object to it:</span>
ptrdiff_t <span class="br0">(</span><span class="sy0">*</span>p_myrandom<span class="br0">)</span><span class="br0">(</span>ptrdiff_t<span class="br0">)</span> <span class="sy0">=</span> myrandom<span class="sy0">;</span>
<span class="kw4">int</span> main <span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
srand <span class="br0">(</span> <span class="kw4">unsigned</span> <span class="br0">(</span> time <span class="br0">(</span>NULL<span class="br0">)</span> <span class="br0">)</span> <span class="br0">)</span><span class="sy0">;</span>
vector<span class="sy0"><</span>int<span class="sy0">></span> myvector<span class="sy0">;</span>
vector<span class="sy0"><</span>int<span class="sy0">>::</span><span class="me2">iterator</span> it<span class="sy0">;</span>
<span class="co1">// set some values:</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i<span class="sy0">=</span><span class="nu0">1</span><span class="sy0">;</span> i<span class="sy0"><</span><span class="nu0">10</span><span class="sy0">;</span> <span class="sy0">++</span>i<span class="br0">)</span> myvector.<span class="me1">push_back</span><span class="br0">(</span>i<span class="br0">)</span><span class="sy0">;</span> <span class="co1">// 1 2 3 4 5 6 7 8 9</span>
<span class="co1">// using built-in random generator:</span>
random_shuffle <span class="br0">(</span> myvector.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> myvector.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">)</span><span class="sy0">;</span>
<span class="co1">// using myrandom:</span>
random_shuffle <span class="br0">(</span> myvector.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> myvector.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> p_myrandom<span class="br0">)</span><span class="sy0">;</span>
<span class="co1">// print out content:</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">"myvector contains:"</span><span class="sy0">;</span>
<span class="kw1">for</span> <span class="br0">(</span>it<span class="sy0">=</span>myvector.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> it<span class="sy0">!=</span>myvector.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> <span class="sy0">++</span>it<span class="br0">)</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">" "</span> <span class="sy0"><<</span> <span class="sy0">*</span>it<span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="kw1">return</span> <span class="nu0">0</span><span class="sy0">;</span>
<span class="br0">}</span></pre>
<p>
A possible output:
myvector contains: 3 4 1 6 8 9 2 7 5
</p>
<p>
Related Topics: <a href="../../stl/algorithm/next_permutation.html" class="wikilink1" title="stl:algorithm:next_permutation">next_permutation</a>, <a href="../../stl/algorithm/prev_permutation.html" class="wikilink1" title="stl:algorithm:prev_permutation">prev_permutation</a>, <a href="../../stl/algorithm/random_sample.html" class="wikilink1" title="stl:algorithm:random_sample">random_sample</a>, <a href="../../stl/algorithm/random_sample_n.html" class="wikilink1" title="stl:algorithm:random_sample_n">random_sample_n</a>
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