📄 prev_permutation.html

📁 指导程序员合理、高效的进行标准模板库编程。
💻 HTML
字号:
<HTML>
<HEAD>
   <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
   <META NAME="Author" CONTENT="Zafir Anjum">
   <TITLE>MFC Programmer's SourceBook : STL Programmer's Guide</TITLE>
    <META name="description" 
     content="A freely available implementation 
     of the C++ Standard Template Library, including 
     hypertext documentation.">
	<META name="keywords" 
	content="generic programming, STL, standard template library">
</HEAD>

<SCRIPT LANGUAGE="JavaScript"><!--
var adcategory = "cpp";
// -->
</SCRIPT>
<body background="../../fancyhome/back.gif" bgcolor="#FFFFFF" >
<SCRIPT LANGUAGE="JavaScript"><!--
var nfrm = location.href.indexOf("_nfrm_");
var validframes = (top.frames.length > 0 && top.frames['ad'] && top.frames['logo'] );
var random = Math.random();

if( !validframes && nfrm == -1 )
{
	var dclkPage = "www.codeguru.com/";
	if( self.adcategory )
		dclkPage += adcategory;
	else
		dclkPage += "mfc";
	document.write('<nolayer><center>');
	document.write('<iframe src="http://ad.doubleclick.net/adi/' + dclkPage + ';ord='
	 + random + '" width=470 height=62 marginwidth=0 marginheight=0 hspace=0 vspace=0 '
	 + 'frameborder=0 scrolling=no bordercolor="#000000">');
	document.write('<a href="http://ad.doubleclick.net/jump/' + dclkPage + ';ord='
	 + random + '">');
	document.write('<img src="http://ad.doubleclick.net/ad/' + dclkPage + ';ord='
	 + random + '" height=60 width=468>' + '</a>');
	document.write('</iframe>');
	document.write('</center></nolayer>');
	document.write('<layer  src="http://ad.doubleclick.net/adl/' + dclkPage + 
	 ';ord=' + random + '"></layer>');
	document.write('<ilayer visibility=hide width=468 height=83></ilayer>');
}


//		top.location = "/show.cgi?" + adcategory + "=" + location.pathname;


// -->
</SCRIPT>
<noscript>
<p align="center">
<a href="http://ad.doubleclick.net/jump/www.codeguru.com/cpp;ord=NupbZ9FCY34AAHWbyQc">
<img src="http://ad.doubleclick.net/ad/www.codeguru.com/cpp;ord=NupbZ9FCY34AAHWbyQc"></a>
</p>
</noscript>





<BR Clear>
<H1>prev_permutation</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>Prev_permutation</tt> is an overloaded name; there are actually two <tt>prev_permutation</tt>
functions.
<pre>
template &lt;class <A href="BidirectionalIterator.html">BidirectionalIterator</A>&gt;
bool prev_permutation(BidirectionalIterator first,
                      BidirectionalIterator last);

template &lt;class <A href="BidirectionalIterator.html">BidirectionalIterator</A>, class <A href="StrictWeakOrdering.html" tppabs="http://www.sgi.com/Technology/STL/StrictWeakOrdering.shtml">StrictWeakOrdering</A>&gt;
bool prev_permutation(BidirectionalIterator first, BidirectionalIterator last,
                      <A href="StrictWeakOrdering.html">StrictWeakOrdering</A> comp);
</pre>                   
<h3>Description</h3>
<tt>Prev_permutation</tt> transforms the range of elements <tt>[first, last)</tt>
into the lexicographically next smaller permutation of the elements.
There is a finite number of distinct permutations (at most
<tt>N!</tt> <A href="#1">[1]</A>, where <tt>N</tt> is <tt>last - first</tt>), so, if the permutations are
ordered by <tt><A href="lexicographical_compare.html">lexicographical_compare</A></tt>, there is an unambiguous
definition of which permutation is lexicographically previous.  If such
a permutation exists, <tt>prev_permutation</tt> transforms <tt>[first, last)</tt>
into that permutation and returns <tt>true</tt>.  Otherwise it transforms
<tt>[first, last)</tt> into the lexicographically greatest permutation <A href="#2">[2]</A>
and returns <tt>false</tt>.  
<P>
The postcondition is that the new permutation of elements is
lexicographically less than the old (as determined by
<tt><A href="lexicographical_compare.html">lexicographical_compare</A></tt>) if and only if the return value is
<tt>true</tt>.
<P>
The two versions of <tt>prev_permutation</tt> differ in how they define
whether one element is less than another.  The first version 
compares objects using <tt>operator&lt;</tt>, and the second compares objects
using a <A href="functors.html">function object</A> <tt>comp</tt>.
<h3>Definition</h3>
Defined in <A href="algo.h">algo.h</A>.
<h3>Requirements on types</h3>
For the first version:
<UL>
<LI>
<tt>BidirectionalIterator</tt> is a model of <A href="BidirectionalIterator.html">Bidirectional Iterator</A>.
<LI>
<tt>BidirectionalIterator</tt> is mutable.
<LI>
<tt>BidirectionalIterator</tt>'s value type is <A href="LessThanComparable.html">LessThan Comparable</A>.
<LI>
The ordering relation on <tt>BidirectionalIterator</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:
<UL>
<LI>
<tt>BidirectionalIterator</tt> is a model of <A href="BidirectionalIterator.html">Bidirectional Iterator</A>.
<LI>
<tt>BidirectionalIterator</tt> is mutable.
<LI>
<tt>StrictWeakOrdering</tt> is a model of <A href="StrictWeakOrdering.html">Strict Weak Ordering</A>.
<LI>
<tt>BidirectionalIterator</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>
Linear.  At most <tt>(last - first) / 2</tt> swaps.
<h3>Example</h3>
<pre>
int main()
{
  int A[] = {2, 3, 4, 5, 6, 1};
  const int N = sizeof(A) / sizeof(int);

  cout &lt;&lt; &quot;Initially:              &quot;;
  <A href="copy.html">copy</A>(A, A+N, <A href="ostream_iterator.html" tppabs="http://www.sgi.com/Technology/STL/ostream_iterator.shtml">ostream_iterator</A>&lt;int&gt;(cout, &quot; &quot;));
  cout &lt;&lt; endl;

  prev_permutation(A, A+N);
  cout &lt;&lt; &quot;After prev_permutation: &quot;;
  <A href="copy.html">copy</A>(A, A+N, <A href="ostream_iterator.html" tppabs="http://www.sgi.com/Technology/STL/ostream_iterator.shtml">ostream_iterator</A>&lt;int&gt;(cout, &quot; &quot;));
  cout &lt;&lt; endl;

  next_permutation(A, A+N);
  cout &lt;&lt; &quot;After next_permutation: &quot;;
  <A href="copy.html">copy</A>(A, A+N, <A href="ostream_iterator.html" tppabs="http://www.sgi.com/Technology/STL/ostream_iterator.shtml">ostream_iterator</A>&lt;int&gt;(cout, &quot; &quot;));
  cout &lt;&lt; endl;
}
</pre>
<h3>Notes</h3>
<P><A name="1">[1]</A>
If all of the elements in <tt>[first, last)</tt> are distinct from each
other, then there are exactly <tt>N!</tt> permutations.  If some elements are
the same as each other, though, then there are fewer.  There are, for
example, only three (<tt>3!/2!</tt>) permutations of the elements <tt>1 1 2</tt>.
<P><A name="2">[2]</A>
Note that the lexicographically greatest permutation is, by
definition, sorted in nonascending order.
<h3>See also</h3>
<tt><A href="next_permutation.html">next_permutation</A></tt>, <tt><A href="lexicographical_compare.html" tppabs="http://www.sgi.com/Technology/STL/lexicographical_compare.shtml">lexicographical_compare</A></tt>, 
<A href="LessThanComparable.html">LessThan Comparable</A>, <A href="StrictWeakOrdering.html" tppabs="http://www.sgi.com/Technology/STL/StrictWeakOrdering.shtml">Strict Weak Ordering</A>, <tt><A href="sort.html" tppabs="http://www.sgi.com/Technology/STL/sort.shtml">sort</A></tt>

<HR SIZE="6"> <FONT SIZE="-2"> Copyright &copy; 1996 Silicon Graphics, Inc.
<HR>
<TABLE BORDER=0 WIDTH="100%" >
<TR>
<TD WIDTH="33%"><FONT SIZE=-1><A HREF="index.html" >
STL</A></FONT></TD>

<TD WIDTH="33%">
<CENTER><FONT SIZE=-2>&copy; Copyright 1997-1998 CodeGuru</FONT>&nbsp;</CENTER>
</TD>

<TD WIDTH="34%">
<DIV ALIGN=right><FONT SIZE=-1>Contact : <A HREF="mailto:webmaster@codeguru.com">webmaster@codeguru.com</A>&nbsp;</FONT></DIV>
</TD>
</TR>
</TABLE>
<SCRIPT LANGUAGE="JavaScript" ><!--
var adurl = "/cgi-bin/doubleclick.cgi?";

if( self.adcategory )
	adurl += adcategory;
else
	adurl += "mfc";

if( self.parent.norefreshad )
	parent.norefreshad = false;
else if( validframes )
	parent.frames['ad'].location = adurl;



if( !validframes && nfrm == -1)
{
	var dclkPage = "www.codeguru.com/";
	if( self.adcategory )
		dclkPage += adcategory;
	else 
		dclkPage += "mfc";
//	var random = Math.random();
	document.write('<nolayer><center>');
	document.write('<iframe src="http://ad.doubleclick.net/adi/' + dclkPage + ';ord='
	 + random + '" width=470 height=62 marginwidth=0 marginheight=0 hspace=0 vspace=0 '
	 + 'frameborder=0 scrolling=no bordercolor="#000000">');
	document.write('<a href="http://ad.doubleclick.net/jump/' + dclkPage + ';ord='
	 + random + '">');
	document.write('<img src="http://ad.doubleclick.net/ad/' + dclkPage + ';ord='
	 + random + '" height=60 width=468>' + '</a>');
	document.write('</iframe>');
	document.write('</center></nolayer>');
	document.write('<layer  src="http://ad.doubleclick.net/adl/' + dclkPage + 
	 ';ord=' + random + '"></layer>');
	document.write('<ilayer visibility=hide width=468 height=83></ilayer>');
}

// -->
</SCRIPT> 
<!-- SCRIPT LANGUAGE="JavaScript" SRC="/global/fscript.js">
//
</SCRIPT --> 

<noscript>
<p align="center">
<a href="http://ad.doubleclick.net/jump/www.codeguru.com/cpp;ord=NupbZ9FCY34AAHWbyQc">
<img src="http://ad.doubleclick.net/ad/www.codeguru.com/cpp;ord=NupbZ9FCY34AAHWbyQc"></a>
</p>
</noscript>





</BODY>
</HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -