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<h2><a name="sort" id="sort">sort</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> sort<span class="br0">(</span> random_iterator start<span class="sy0">,</span> random_iterator end <span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">void</span> sort<span class="br0">(</span> random_iterator start<span class="sy0">,</span> random_iterator end<span class="sy0">,</span> StrictWeakOrdering cmp <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The sort() algorithm sorts the elements in the range <code>[start,end)</code> into ascending
order. If two elements are equal, there is no guarantee what order they will be
in.
</p>
<p>
If the strict weak ordering function object <code>cmp</code> is given, then it will be used
to compare two objects instead of the <code><</code> operator.
</p>
<p>
The algorithm behind sort() is the introsort algorithm. sort() runs in O(N log
(N)) time (average and worst case) which is faster than polynomial time but
slower than <a href="../../complexity.html" class="wikilink1" title="complexity">linear time</a>.
</p>
<p>
Note that sort() will only work with random access iterators. So you cannot use
sort() on the iterators of a “list” (linked list). Instead, you should use list's
own <a href="../../stl/list/sort.html" class="wikilink1" title="stl:list:sort">sort</a> method to sort it instead.
</p>
<p>
For example, the following code sorts a vector of integers into ascending
order:
</p>
<pre class="c code c++" style="font-family:monospace;"> vector<span class="sy0"><</span>int<span class="sy0">></span> v<span class="sy0">;</span>
v.<span class="me1">push_back</span><span class="br0">(</span> 23 <span class="br0">)</span><span class="sy0">;</span>
v.<span class="me1">push_back</span><span class="br0">(</span> <span class="sy0">-</span>1 <span class="br0">)</span><span class="sy0">;</span>
v.<span class="me1">push_back</span><span class="br0">(</span> 9999 <span class="br0">)</span><span class="sy0">;</span>
v.<span class="me1">push_back</span><span class="br0">(</span> 0 <span class="br0">)</span><span class="sy0">;</span>
v.<span class="me1">push_back</span><span class="br0">(</span> 4 <span class="br0">)</span><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> <span class="st0">"Before sorting: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">unsigned</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> v.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <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> v<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<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> endl<span class="sy0">;</span>
sort<span class="br0">(</span> v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> v.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">)</span><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> <span class="st0">"After sorting: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">unsigned</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> v.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <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> v<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<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> endl<span class="sy0">;</span></pre>
<p>
When run, the above code displays this output:
</p>
<pre class="code">
Before sorting: 23 -1 9999 0 4
After sorting: -1 0 4 23 9999</pre>
<p>
Alternatively, the following code uses the sort() function to sort a normal
array of integers, and displays the same output as the previous example:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw4">int</span> array<span class="br0">[</span><span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span> 23<span class="sy0">,</span> <span class="sy0">-</span>1<span class="sy0">,</span> 9999<span class="sy0">,</span> 0<span class="sy0">,</span> 4 <span class="br0">}</span><span class="sy0">;</span>
<span class="kw4">unsigned</span> <span class="kw4">int</span> array_size <span class="sy0">=</span> <span class="nu0">5</span><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> <span class="st0">"Before sorting: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">unsigned</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> array_size<span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <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> array<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<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> endl<span class="sy0">;</span>
sort<span class="br0">(</span> array<span class="sy0">,</span> array <span class="sy0">+</span> array_size <span class="br0">)</span><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> <span class="st0">"After sorting: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">unsigned</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> array_size<span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <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> array<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<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> endl<span class="sy0">;</span></pre>
<p>
This next example shows how to use sort() with a user-specified comparison
function. The function <code>cmp</code> is defined to do the opposite of the <code><</code> operator.
When sort() is called with <code>cmp</code> used as the comparison function, the result is a
list sorted in descending, rather than ascending, order:
</p>
<pre class="c code c++" style="font-family:monospace;"> bool cmp<span class="br0">(</span> <span class="kw4">int</span> a<span class="sy0">,</span> <span class="kw4">int</span> b <span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">return</span> a <span class="sy0">></span> b<span class="sy0">;</span>
<span class="br0">}</span>
...
<span class="me1">vector</span><span class="sy0"><</span>int<span class="sy0">></span> v<span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> <span class="nu0">10</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <span class="br0">{</span>
v.<span class="me1">push_back</span><span class="br0">(</span>i<span class="br0">)</span><span class="sy0">;</span>
<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">"Before: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> <span class="nu0">10</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <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> v<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<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> endl<span class="sy0">;</span>
sort<span class="br0">(</span> v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> v.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> cmp <span class="br0">)</span><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> <span class="st0">"After: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">int</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> <span class="nu0">10</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <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> v<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<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> endl<span class="sy0">;</span></pre>
<p>
Related Topics: <a href="../../stl/algorithm/binary_search.html" class="wikilink1" title="stl:algorithm:binary_search">binary_search</a>, <a href="../../stl/algorithm/merge.html" class="wikilink1" title="stl:algorithm:merge">merge</a>, <a href="../../stl/algorithm/partial_sort.html" class="wikilink1" title="stl:algorithm:partial_sort">partial_sort</a>, <a href="../../stl/algorithm/partial_sort_copy.html" class="wikilink1" title="stl:algorithm:partial_sort_copy">partial_sort_copy</a>, <a href="../../stl/algorithm/stable_sort.html" class="wikilink1" title="stl:algorithm:stable_sort">stable_sort</a>, <a href="../../c/other/qsort.html" class="wikilink1" title="c:other:qsort">qsort</a>
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