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   4   Algorithms
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   7   Standard Contents
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   9   Algorithms
  10   <a id="id505811" class="indexterm"></a>
  11 </h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="algorithms.html#std.algorithms.mutating">Mutating</a></span></dt><dd><dl><dt><span class="sect2"><a href="algorithms.html#algorithms.mutating.swap"><code class="function">swap</code></a></span></dt></dl></dd></dl></div><p>
  12   The neatest accomplishment of the algorithms sect1 is that all the
  13   work is done via iterators, not containers directly.  This means two
  14   important things:
  15 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
  16       Anything that behaves like an iterator can be used in one of
  17       these algorithms.  Raw pointers make great candidates, thus
  18       built-in arrays are fine containers, as well as your own
  19       iterators.
  20     </p></li><li class="listitem"><p>
  21       The algorithms do not (and cannot) affect the container as a
  22       whole; only the things between the two iterator endpoints.  If
  23       you pass a range of iterators only enclosing the middle third of
  24       a container, then anything outside that range is inviolate.
  25     </p></li></ol></div><p>
  26   Even strings can be fed through the algorithms here, although the
  27   string class has specialized versions of many of these functions
  28   (for example, <code class="code">string::find()</code>).  Most of the examples
  29   on this page will use simple arrays of integers as a playground
  30   for algorithms, just to keep things simple.  The use of
  31   <span class="emphasis"><em>N</em></span> as a size in the examples is to keep things
  32   easy to read but probably won't be valid code.  You can use wrappers
  33   such as those described in
  34   the <a class="link" href="containers.html" title="Chapter 9.  Containers">containers sect1</a> to keep
  35   real code readable.
  36 </p><p>
  37   The single thing that trips people up the most is the definition
  38   of <span class="emphasis"><em>range</em></span> used with iterators; the famous
  39   "past-the-end" rule that everybody loves to hate.  The
  40   <a class="link" href="iterators.html" title="Chapter 10.  Iterators">iterators sect1</a> of this
  41     document has a complete explanation of this simple rule that seems
  42     to cause so much confusion.  Once you
  43     get <span class="emphasis"><em>range</em></span> into your head (it's not that hard,
  44     honest!), then the algorithms are a cakewalk.
  45 </p><div class="sect1" title="Mutating"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.algorithms.mutating"></a>Mutating</h2></div></div></div><div class="sect2" title="swap"><div class="titlepage"><div><div><h3 class="title"><a id="algorithms.mutating.swap"></a><code class="function">swap</code></h3></div></div></div><div class="sect3" title="Specializations"><div class="titlepage"><div><div><h4 class="title"><a id="algorithms.swap.specializations"></a>Specializations</h4></div></div></div><p>If you call <code class="code"> std::swap(x,y); </code> where x and y are standard
  46       containers, then the call will automatically be replaced by a call to
  47       <code class="code"> x.swap(y); </code> instead.
  48    </p><p>This allows member functions of each container class to take over, and
  49       containers' swap functions should have O(1) complexity according to
  50       the standard.  (And while "should" allows implementations to
  51       behave otherwise and remain compliant, this implementation does in
  52       fact use constant-time swaps.)  This should not be surprising, since
  53       for two containers of the same type to swap contents, only some
  54       internal pointers to storage need to be exchanged.
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