1*36ac495dSmrg<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2*36ac495dSmrg<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 11. Algorithms</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="ISO C++, library, algorithm" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="std_contents.html" title="Part II. Standard Contents" /><link rel="prev" href="iterators.html" title="Chapter 10. Iterators" /><link rel="next" href="numerics.html" title="Chapter 12. Numerics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 11. 3*36ac495dSmrg Algorithms 4*36ac495dSmrg 5*36ac495dSmrg</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="iterators.html">Prev</a> </td><th width="60%" align="center">Part II. 6*36ac495dSmrg Standard Contents 7*36ac495dSmrg </th><td width="20%" align="right"> <a accesskey="n" href="numerics.html">Next</a></td></tr></table><hr /></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="std.algorithms"></a>Chapter 11. 8*36ac495dSmrg Algorithms 9*36ac495dSmrg <a id="id-1.3.4.9.1.1.1" class="indexterm"></a> 10*36ac495dSmrg</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="section"><a href="algorithms.html#std.algorithms.mutating">Mutating</a></span></dt><dd><dl><dt><span class="section"><a href="algorithms.html#algorithms.mutating.swap"><code class="function">swap</code></a></span></dt><dd><dl><dt><span class="section"><a href="algorithms.html#algorithms.swap.specializations">Specializations</a></span></dt></dl></dd></dl></dd></dl></div><p> 11*36ac495dSmrg The neatest accomplishment of the algorithms section is that all the 12*36ac495dSmrg work is done via iterators, not containers directly. This means two 13*36ac495dSmrg important things: 14*36ac495dSmrg</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p> 15*36ac495dSmrg Anything that behaves like an iterator can be used in one of 16*36ac495dSmrg these algorithms. Raw pointers make great candidates, thus 17*36ac495dSmrg built-in arrays are fine containers, as well as your own 18*36ac495dSmrg iterators. 19*36ac495dSmrg </p></li><li class="listitem"><p> 20*36ac495dSmrg The algorithms do not (and cannot) affect the container as a 21*36ac495dSmrg whole; only the things between the two iterator endpoints. If 22*36ac495dSmrg you pass a range of iterators only enclosing the middle third of 23*36ac495dSmrg a container, then anything outside that range is inviolate. 24*36ac495dSmrg </p></li></ol></div><p> 25*36ac495dSmrg Even strings can be fed through the algorithms here, although the 26*36ac495dSmrg string class has specialized versions of many of these functions 27*36ac495dSmrg (for example, <code class="code">string::find()</code>). Most of the examples 28*36ac495dSmrg on this page will use simple arrays of integers as a playground 29*36ac495dSmrg for algorithms, just to keep things simple. The use of 30*36ac495dSmrg <span class="emphasis"><em>N</em></span> as a size in the examples is to keep things 31*36ac495dSmrg easy to read but probably won't be valid code. You can use wrappers 32*36ac495dSmrg such as those described in 33*36ac495dSmrg the <a class="link" href="containers.html" title="Chapter 9. Containers">containers section</a> to keep 34*36ac495dSmrg real code readable. 35*36ac495dSmrg</p><p> 36*36ac495dSmrg The single thing that trips people up the most is the definition 37*36ac495dSmrg of <span class="emphasis"><em>range</em></span> used with iterators; the famous 38*36ac495dSmrg "past-the-end" rule that everybody loves to hate. The 39*36ac495dSmrg <a class="link" href="iterators.html" title="Chapter 10. Iterators">iterators section</a> of this 40*36ac495dSmrg document has a complete explanation of this simple rule that seems 41*36ac495dSmrg to cause so much confusion. Once you 42*36ac495dSmrg get <span class="emphasis"><em>range</em></span> into your head (it's not that hard, 43*36ac495dSmrg honest!), then the algorithms are a cakewalk. 44*36ac495dSmrg</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.algorithms.mutating"></a>Mutating</h2></div></div></div><div class="section"><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="section"><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 45*36ac495dSmrg containers, then the call will automatically be replaced by a call to 46*36ac495dSmrg <code class="code"> x.swap(y); </code> instead. 47*36ac495dSmrg </p><p>This allows member functions of each container class to take over, and 48*36ac495dSmrg containers' swap functions should have O(1) complexity according to 49*36ac495dSmrg the standard. (And while "should" allows implementations to 50*36ac495dSmrg behave otherwise and remain compliant, this implementation does in 51*36ac495dSmrg fact use constant-time swaps.) This should not be surprising, since 52*36ac495dSmrg for two containers of the same type to swap contents, only some 53*36ac495dSmrg internal pointers to storage need to be exchanged. 54*36ac495dSmrg </p></div></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="iterators.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="std_contents.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="numerics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 10. 55*36ac495dSmrg Iterators 56*36ac495dSmrg 57*36ac495dSmrg </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 12. 58*36ac495dSmrg Numerics 59*36ac495dSmrg 60*36ac495dSmrg</td></tr></table></div></body></html>