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<HEAD>
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<TITLE>partial_sort_copy()</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="partial-sort.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="partial-sum.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>partial_sort_copy()</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>Templatized algorithm for sorting collections of entities</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 InputIterator,
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class RandomAccessIterator>
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void partial_sort_copy(InputIterator start,
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InputIterator finish,
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RandomAccessIterator result_start,
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RandomAccessIterator result_finish);
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template <class InputIterator,
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class RandomAccessIterator,
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class Compare>
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void partial_sort_copy(InputIterator start,
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InputIterator finish,
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RandomAccessIterator result_start,
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RandomAccessIterator result_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 <SAMP>partial_sort_copy()</SAMP> algorithm places the smaller of <SAMP>finish - start</SAMP> and <SAMP>result_finish - result_start</SAMP> sorted elements from the range <SAMP>[start, finish)</SAMP> into the range beginning at <SAMP>result_start</SAMP> (in other words, the range: <SAMP>[result_start, result_start+min(finish - start, result_finish - result_start)</SAMP>). The effect is as if the range <SAMP>[start,finish)</SAMP> were placed in a temporary buffer, sorted, and then as many elements as possible copied into the range <SAMP>[result_start, result_finish)</SAMP>.</P>
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<P>The first version of the algorithm uses <SAMP>operator<()</SAMP> as the comparison operator for the sort. The second version uses the function object <SAMP>comp.</SAMP></P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P><SAMP>partial_sort_copy()</SAMP> does approximately<SAMP> (finish-start) * log(min(finish-start, result_finish-result_start))</SAMP> comparisons.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// partsort.cpp
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//
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#include <algorithm> // for partial_sort
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#include <iostream> // for cout, endl
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#include <iterator> // for ostream_iterator
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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> > Vector;
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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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const Vector::value_type a[] = {
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17, 3, 5, -4, 1, 12, -10, -1, 14, 7,
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-6, 8, 15, -11, 2, -2, 18, 4, -3, 0
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};
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Vector v1 (a + 0, a + sizeof a / sizeof *a);
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// Output original vector.
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std::cout << "For the vector: ";
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std::copy (v1.begin (), v1.end (), Iter (std::cout, " "));
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// Partial sort the first seven elements.
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std::partial_sort (v1.begin (), v1.begin () + 7,
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v1.end ());
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// Output result.
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std::cout << "\n\nA partial_sort of seven elements "
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<< "gives: \n ";
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std::copy (v1.begin (), v1.end (), Iter (std::cout, " "));
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std::cout << std::endl;
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// A vector of ten elements.
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Vector v2 (Vector::size_type (10), 0);
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// Sort the last ten elements in v1 into v2.
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std::partial_sort_copy (v1.begin () + 10, v1.end (),
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v2.begin (), v2.end ());
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// Output result.
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std::cout
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<< "\nA partial_sort_copy of the last ten elements "
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<< "gives: \n ";
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std::copy (v2.begin (), v2.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 Output:
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For the vector: 17 3 5 -4 1 12 -10 -1 14 7 -6 8 15 -11 2 -2
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18 4 -3 0
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A partial_sort of seven elements gives:
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-11 -10 -6 -4 -3 -2 -1 17 14 12 7 8 15 5 3 2 18 4 1 0
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A partial_sort_copy of the last ten elements gives:
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0 1 2 3 4 5 7 8 15 18
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</PRE></UL>
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<UL><PRE></PRE></UL>
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<A NAME="sec7"><H3>See Also</H3></A>
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<P><SAMP><A HREF="sort.html">sort()</A></SAMP>¸ <SAMP><A HREF="stable-sort.html">stable_sort()</A></SAMP>, <SAMP><A HREF="partial-sort.html">partial_sort()</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 25.3.1.4</I></P>
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