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<html><head><title>sort (Perl in a Nutshell, 2nd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Stephen Spainhour" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="0596002416L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl in a Nutshell, 2nd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Java and XSLT" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_187.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch08_189.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.188. sort</h2><p><a name="INDEX-1552" />The<tt class="literal">sort</tt> pragma allows you to control<tt class="literal">sort()</tt> behavior. In Perl 5.6 and earlier, thedefault <tt class="literal">sort()</tt> behavior was written with<tt class="literal">quicksort</tt>. Perl 5.8, with which<em class="filename">sort.pm</em> is shipped in the source kit, implements<tt class="literal">mergesort</tt>. <tt class="literal">mergesort</tt> guaranteesthe worst-case behavior of <tt class="literal">O(N log N)</tt>, where<tt class="literal">quicksort</tt> guarantees <tt class="literal">O(N ** 2)</tt>.</p><p>Perl 5.8 and later shuffle large arrays before sorting. Note that<em class="filename">sort.pm</em> is global and not lexical in scope.</p><p>For example:</p><blockquote><pre class="code">#!/usr/local/bin/perl -wuse sort '_quicksort'; # Or _qsort, if you'd likesort(@something);</pre></blockquote><p><tt class="literal">mergesort</tt> is better than<tt class="literal">quicksort</tt> for several reasons. First,<tt class="literal">mergesort</tt> is more stable and does fewercomparisons than <tt class="literal">quicksort</tt>, soit's better for more complicated sorting routines.In addition, <tt class="literal">mergesort</tt> takes preexisting orderinto account.</p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_187.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch08_189.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.187. Socket</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">8.189. Storable</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"><area shape="rect" coords="1,0,85,94" href="../index.htm"><area shape="rect" coords="86,1,178,103" href="../lwp/index.htm"><area shape="rect" coords="180,0,265,103" href="../lperl/index.htm"><area shape="rect" coords="267,0,353,105" href="../perlnut/index.htm"><area shape="rect" coords="354,1,446,115" href="../prog/index.htm"><area shape="rect" coords="448,0,526,132" href="../tk/index.htm"><area shape="rect" coords="528,1,615,119" href="../cookbook/index.htm"><area shape="rect" coords="617,0,690,135" href="../pxml/index.htm"></map></body></html>⌨️ 快捷键说明
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