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<HTML><!-- -- Copyright (c) 1996-1999 -- Silicon Graphics Computer Systems, Inc. -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Silicon Graphics makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- -- Copyright (c) 1994 -- Hewlett-Packard Company -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. 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It is provided "as is" without express or implied warranty. -- --><Head><Title>sort</Title><!-- Generated by htmldoc --></HEAD><BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="CorpID.gif" ALT="SGI" HEIGHT="43" WIDTH="151"> <!--end header--><BR Clear><H1>sort</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "algorithms.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: algorithms</TD><TD Align=right VAlign=top><b>Component type</b>: function</TD></TR></Table><h3>Prototype</h3><tt>Sort</tt> is an overloaded name; there are actually two <tt>sort</tt>functions.<pre>template <class <A href="RandomAccessIterator.html">RandomAccessIterator</A>>void sort(RandomAccessIterator first, RandomAccessIterator last);template <class RandomAccessIterator, class <A href="StrictWeakOrdering.html">StrictWeakOrdering</A>>void sort(RandomAccessIterator first, RandomAccessIterator last, StrictWeakOrdering comp);</pre> <h3>Description</h3><tt>Sort</tt> sorts the elements in <tt>[first, last)</tt> into ascending order,meaning that if <tt>i</tt> and <tt>j</tt> are any two valid iterators in <tt>[first, last)</tt>such that <tt>i</tt> precedes <tt>j</tt>, then <tt>*j</tt> is not less than <tt>*i</tt>. Note:<tt>sort</tt> is not guaranteed to be stable. That is, suppose that <tt>*i</tt>and <tt>*j</tt> are equivalent: neither one is less than the other. It isnot guaranteed that the relative order of these two elements will bepreserved by <tt>sort</tt>. <A href="#1">[1]</A><P>The two versions of <tt>sort</tt> differ in how they define whether oneelement is less than another. The first version comparesobjects using <tt>operator<</tt>, and the second compares objects usinga <A href="functors.html">function object</A> <tt>comp</tt>.<h3>Definition</h3>Defined in the standard header <A href="algorithm">algorithm</A>, and in the nonstandardbackward-compatibility header <A href="algo.h">algo.h</A>.<h3>Requirements on types</h3>For the first version, the one that takes two arguments:<UL><LI><tt>RandomAccessIterator</tt> is a model of <A href="RandomAccessIterator.html">Random Access Iterator</A>.<LI><tt>RandomAccessIterator</tt> is mutable.<LI><tt>RandomAccessIterator</tt>'s value type is <A href="LessThanComparable.html">LessThan Comparable</A>.<LI>The ordering relation on <tt>RandomAccessIterator</tt>'s value type is a <i>strict weak ordering</i>, as defined in the <A href="LessThanComparable.html">LessThan Comparable</A> requirements.</UL>For the second version, the one that takes three arguments:<UL><LI><tt>RandomAccessIterator</tt> is a model of <A href="RandomAccessIterator.html">Random Access Iterator</A>.<LI><tt>RandomAccessIterator</tt> is mutable.<LI><tt>StrictWeakOrdering</tt> is a model of <A href="StrictWeakOrdering.html">Strict Weak Ordering</A>.<LI><tt>RandomAccessIterator</tt>'s value type is convertible to <tt>StrictWeakOrdering</tt>'s argument type.</UL><h3>Preconditions</h3><UL><LI><tt>[first, last)</tt> is a valid range.</UL><h3>Complexity</h3><tt>O(N log(N))</tt> comparisons (both average and worst-case), where <tt>N</tt> is <tt>last - first</tt>. <A href="#2">[2]</A><h3>Example</h3><pre>int A[] = {1, 4, 2, 8, 5, 7};const int N = sizeof(A) / sizeof(int);sort(A, A + N);copy(A, A + N, ostream_iterator<int>(cout, " "));// The output is " 1 2 4 5 7 8".</pre><h3>Notes</h3><P><A name="1">[1]</A>Stable sorting is sometimes important if you are sorting recordsthat have multiple fields: you might, for example, want to sort a listof people by first name and then by last name. The algorithm <tt><A href="stable_sort.html">stable_sort</A></tt> does guarantee to preserve the relative orderingof equivalent elements.<P><A name="2">[2]</A>Earlier versions of <tt>sort</tt> used the <i>quicksort</i> algorithm (C. A. R. Hoare,<i>Comp. J.</i> <b>5</b>, 1962), using a pivot chosen by median of three (R. C. Singleton, <i>CACM</i> <b>12</b>, 1969). Quicksort has<tt>O(N log(N))</tt> average complexity, but quadratic worst-casecomplexity. See section 5.2.2 of Knuth for a discussion. (D. E. Knuth, <i>The Art of Computer Programming. Volume 3: Sorting and Searching</i>. Addison-Wesley, 1975.) The current implementationof <tt>sort</tt>, however, uses the <i>introsort</i> algorithm (D. R.Musser, "Introspective Sorting and Selection Algorithms", <i>Software Practice and Experience</i> <b>27</b>(8):983, 1997.)whose worst case complexity is <tt>O(N log(N))</tt>.Introsort is very similar to median-of-three quicksort, and is atleast as fast as quicksort on average.<h3>See also</h3><tt><A href="stable_sort.html">stable_sort</A></tt>,<tt><A href="partial_sort.html">partial_sort</A></tt>,<tt><A href="partial_sort_copy.html">partial_sort_copy</A></tt>,<tt><A href="sort_heap.html">sort_heap</A></tt>,<tt><A href="is_sorted.html">is_sorted</A></tt>,<tt><A href="binary_search.html">binary_search</A></tt>,<tt><A href="lower_bound.html">lower_bound</A></tt>,<tt><A href="upper_bound.html">upper_bound</A></tt>,<tt><A href="less.html">less</A><T></tt>,<A href="StrictWeakOrdering.html">StrictWeakOrdering</A>,<A href="LessThanComparable.html">LessThan Comparable</A><!--start footer--> <HR SIZE="6"><A href="http://www.sgi.com/"><IMG SRC="surf.gif" HEIGHT="54" WIDTH="54" ALT="[Silicon Surf]"></A><A HREF="index.html"><IMG SRC="stl_home.gif" HEIGHT="54" WIDTH="54" ALT="[STL Home]"></A><BR><FONT SIZE="-2"><A href="http://www.sgi.com/Misc/sgi_info.html" TARGET="_top">Copyright © 1999 Silicon Graphics, Inc.</A> All Rights Reserved.</FONT><FONT SIZE="-3"><a href="http://www.sgi.com/Misc/external.list.html" TARGET="_top">TrademarkInformation</A></FONT><P></BODY></HTML> ?? 快捷鍵說(shuō)明
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