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151 lines
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<HTML>
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<HEAD>
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<TITLE>stable_partition()</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="sstream-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="stable-sort.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>stable_partition()</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>An algorithm that places all of the entities that satisfy the given predicate before all of the entities that do not, while maintaining the relative order of elements in each group</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, class Predicate>
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BidirectionalIterator
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stable_partition(BidirectionalIterator start,
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BidirectionalIterator finish,
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Predicate pred);
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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>For the range <SAMP>[start, finish)</SAMP>, the <SAMP>stable_partition()</SAMP> algorithm places all elements that satisfy <SAMP>pred</SAMP> before all elements that do not satisfy it. It returns an iterator <SAMP>i</SAMP> that is one past the end of the group of elements that satisfies <SAMP>pred</SAMP>. The relative order of the elements in both groups is maintained. </P>
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<P>The <SAMP><A HREF="partition.html">partition()</A></SAMP> algorithm can be used when it is not necessary to maintain the relative order of elements within the groups that do and do not match the predicate.</P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P>The <SAMP>stable_partition()</SAMP> algorithm does at most <SAMP>(finish - start) * log(finish - start)</SAMP> swaps and applies the predicate exactly <SAMP>finish - start</SAMP> times. </P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// prtition.cpp
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//
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#include <algorithm> // for copy
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#include <deque> // for deque
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#include <functional> // for unary_function
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#include <iostream> // for cout, endl
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#include <iterator> // for ostream_iterator
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// Create a new predicate from unary_function.
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template <class Arg>
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struct is_even : public std::unary_function<Arg, bool>
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{
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bool operator()(const Arg &arg1) const {
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return (arg1 % 2) == 0;
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}
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};
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int main ()
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{
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typedef std::deque<int, std::allocator<int> > Deque;
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typedef std::ostream_iterator<int, char,
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std::char_traits<char> >
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Iter;
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// Initialize a deque with an array of integers.
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const Deque::value_type a[] = { 1, 2, 3, 4, 5,
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6, 7, 8, 9, 10 };
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Deque d1 (a + 0, a + sizeof a / sizeof *a);
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Deque d2 (d1);
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// Print out the original values.
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std::cout << "Unpartitioned values: \t\t";
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std::copy (d1.begin (), d1.end (), Iter (std::cout, " "));
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// A partition of the deque according to even/oddness.
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std::partition (d2.begin (), d2.end (), is_even<int>());
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// Output result of partition.
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std::cout << "\nPartitioned values: \t\t";
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std::copy (d2.begin (), d2.end (), Iter (std::cout, " "));
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// A stable partition of the deque according to
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// even/oddness.
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std::stable_partition (d1.begin (), d1.end (),
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is_even<int>());
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// Output result of partition.
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std::cout << "\nStable partitioned values: \t";
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std::copy (d1.begin (), d1.end (), Iter (std::cout, " "));
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std::cout << std::endl;
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return 0;
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}
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Program Files:
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</PRE></UL>
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<UL><PRE>Unpartitioned values: 1 2 3 4 5 6 7 8 9 10
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Partitioned values: 10 2 8 4 6 5 7 3 9 1
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Stable partitioned values: 2 4 6 8 10 1 3 5 7 9
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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="partition.html">partition()</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 25.2.12</I></P>
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