1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
|
<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. Hewlett-Packard Company makes no
-- representations about the suitability of this software for any
-- purpose. 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 is
not guaranteed that the relative order of these two elements will be
preserved by <tt>sort</tt>. <A href="#1">[1]</A>
<P>
The two versions of <tt>sort</tt> differ in how they define whether one
element is less than another. The first version compares
objects using <tt>operator<</tt>, and the second compares objects using
a <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 nonstandard
backward-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 records
that have multiple fields: you might, for example, want to sort a list
of 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 ordering
of 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-case
complexity. 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 implementation
of <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 at
least 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>
|
