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191 lines
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<TITLE>next_permutation()</TITLE>
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<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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<A HREF="new-h.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="not1.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library Reference Guide</B></DIV>
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<H2>next_permutation()</H2>
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<P><B>Library:</B> <A HREF="2-9.html">Algorithms</A></P>
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<PRE><HR><B><I>Function</I></B><HR></PRE>
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<UL>
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<LI><A HREF="#sec1">Local Index</A></LI>
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<LI><A HREF="#sec2">Summary</A></LI>
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<LI><A HREF="#sec3">Synopsis</A></LI>
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<LI><A HREF="#sec4">Description</A></LI>
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<LI><A HREF="#sec5">Complexity</A></LI>
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<LI><A HREF="#sec6">Example</A></LI>
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<LI><A HREF="#sec7">See Also</A></LI>
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<LI><A HREF="#sec8">Standards Conformance</A></LI>
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</UL>
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<A NAME="sec1"><H3>Local Index</H3></A>
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No Entries
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<A NAME="sec2"><H3>Summary</H3></A>
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<P>Algorithm that generates successive permutations of a sequence based on an ordering function </P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <algorithm>
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namespace std {
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template <class BidirectionalIterator>
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bool next_permutation(BidirectionalIterator start,
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BidirectionalIterator finish);
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template <class BidirectionalIterator, class Compare>
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bool next_permutation(BidirectionalIterator start,
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BidirectionalIterator finish,
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Compare comp);
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}
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</PRE>
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<A NAME="sec4"><H3>Description</H3></A>
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<P>The permutation-generating algorithms, <SAMP>next_permutation()</SAMP> and <SAMP><A HREF="prev-permutation.html">prev_permutation()</A></SAMP>, assume that the set of all permutations of the elements in a sequence is lexicographically sorted with respect to <SAMP>operator<()</SAMP> or the binary predicate <SAMP>comp</SAMP>. For example, if a sequence includes the integers 1 2 3, that sequence has six permutations. In order from first to last, they are: 1 2 3, 1 3 2, 2 1 3, 2 3 1, 3 1 2, and 3 2 1. </P>
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<P>The <SAMP>next_permutation()</SAMP> algorithm takes a sequence defined by the range <SAMP>[start, finish)</SAMP> and transforms it into its next permutation, if possible. If such a permutation does exist, the algorithm completes the transformation and returns <SAMP>true</SAMP>. If the permutation does not exist, <SAMP>next_permutation()</SAMP> transforms the permutation into its "first" permutation and returns <SAMP>false</SAMP>. <SAMP>next_permutation()</SAMP> does the transformation according to the lexicographical ordering defined by either <SAMP>operator<()</SAMP> (used in the first version of the algorithm) or the binary predicate <SAMP>comp</SAMP> (which is user-supplied in the second version of the algorithm). </P>
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<P>For example, if the sequence defined by <SAMP>[start, finish)</SAMP> contains the integers 3 2 1 (in that order), there is <I>not</I> a "next permutation." Therefore, the algorithm transforms the sequence into its first permutation (1 2 3) and returns <SAMP>false</SAMP>.</P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P>At most <SAMP>(finish - start)/2 </SAMP>swaps are performed.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// permute.cpp
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//
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#include <algorithm> // for next_permutation, prev_permutation
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#include <functional> // for less
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#include <iostream> // for cout, endl
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#include <numeric> // for accumulate
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#include <vector> // for vector
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int main ()
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{
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typedef std::vector<int, std::allocator<int> > IntVec;
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typedef std::vector<char, std::allocator<char> > CharVec;
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// Initialize a vector using an array of integers.
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const IntVec::value_type a1[] = { 0, 0, 0, 0, 1,
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0, 0, 0, 0, 0 };
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const CharVec::value_type a2[] = "abcdefghji";
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// Create the initial set and copies for permuting.
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IntVec m1 (a1, a1 + sizeof a1 / sizeof *a1);
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IntVec prev_m1 (10);
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IntVec next_m1 (10);
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CharVec m2 (a2, a2 + sizeof a2 / sizeof *a2 - 1);
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CharVec prev_m2 (10);
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CharVec next_m2 (10);
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std::copy (m1.begin (), m1.end (), prev_m1.begin ());
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std::copy (m1.begin (), m1.end (), next_m1.begin ());
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std::copy (m2.begin (), m2.end (), prev_m2.begin ());
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std::copy (m2.begin (), m2.end (), next_m2.begin ());
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// Create permutations.
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typedef std::less<IntVec::value_type> IntLess;
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typedef std::less<CharVec::value_type> CharLess;
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std::prev_permutation (prev_m1.begin (), prev_m1.end (),
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IntLess ());
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std::next_permutation (next_m1.begin (), next_m1.end (),
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IntLess ());
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std::prev_permutation (prev_m2.begin (), prev_m2.end (),
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CharLess ());
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std::next_permutation (next_m2.begin (), next_m2.end (),
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CharLess ());
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// Output results.
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typedef std::ostream_iterator<IntVec::value_type, char,
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std::char_traits<char> >
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IntOSIter;
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typedef std::ostream_iterator<CharVec::value_type, char,
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std::char_traits<char> >
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CharOSIter;
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std::cout << "Example 1: \n Original values: ";
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std::copy (m1.begin (), m1.end (),
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IntOSIter (std::cout, " "));
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std::cout << "\n Previous permutation: ";
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std::copy (prev_m1.begin (), prev_m1.end (),
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IntOSIter (std::cout, " "));
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std::cout << "\n Next Permutation: ";
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std::copy (next_m1.begin (), next_m1.end (),
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IntOSIter (std::cout, " "));
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std::cout << "\n\nExample 2: \n ";
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<< "Original values: ";
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std::copy (m2.begin (), m2.end (),
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CharOSIter (std::cout, " "));
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std::cout << "\n Previous Permutation: ";
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std::copy (prev_m2.begin (), prev_m2.end (),
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CharOSIter (std::cout, " "));
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std::cout << "\n Next Permutation: ";
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std::copy (next_m2.begin (), next_m2.end (),
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CharOSIter (std::cout, " "));
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std::cout << std::endl << std::endl;
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return 0;
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}
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Program Output:
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</PRE></UL>
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<UL><PRE>Example 1:
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Original values: 0 0 0 0 1 0 0 0 0 0
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Previous permutation: 0 0 0 0 0 1 0 0 0 0
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Next Permutation: 0 0 0 1 0 0 0 0 0 0
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Example 2:
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Original values: a b c d e f g h j i
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Previous Permutation: a b c d e f g h i j
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Next Permutation: a b c d e f g i h j
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</PRE></UL>
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<A NAME="sec7"><H3>See Also</H3></A>
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<P><SAMP><A HREF="prev-permutation.html">prev_permutation()</A></SAMP></P>
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<A NAME="sec8"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.9</I></P>
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<BR>
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