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| <TITLE>partial_sort()</TITLE> |
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| <A HREF="pair.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-sort-copy.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> |
| <H2>partial_sort()</H2> |
| <P><B>Library:</B> <A HREF="2-9.html">Algorithms</A></P> |
| |
| <PRE><HR><B><I>Function</I></B><HR></PRE> |
| |
| <UL> |
| <LI><A HREF="#sec1">Local Index</A></LI> |
| <LI><A HREF="#sec2">Summary</A></LI> |
| <LI><A HREF="#sec3">Synopsis</A></LI> |
| <LI><A HREF="#sec4">Description</A></LI> |
| <LI><A HREF="#sec5">Complexity</A></LI> |
| <LI><A HREF="#sec6">Example</A></LI> |
| <LI><A HREF="#sec7">See Also</A></LI> |
| <LI><A HREF="#sec8">Standards Conformance</A></LI> |
| </UL> |
| <A NAME="sec1"><H3>Local Index</H3></A> |
| No Entries |
| <A NAME="sec2"><H3>Summary</H3></A> |
| <P>A generic algorithm for sorting collections of entities</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <algorithm> |
| |
| namespace std { |
| template <class RandomAccessIterator> |
| void partial_sort(RandomAccessIterator start, |
| RandomAccessIterator mid, |
| RandomAccessIterator finish); |
| |
| template <class RandomAccessIterator, class Compare> |
| void partial_sort(RandomAccessIterator start, |
| RandomAccessIterator mid, |
| RandomAccessIterator finish, |
| Compare comp); |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <P>The <SAMP>partial_sort()</SAMP> algorithm takes the range <SAMP>[start,finish)</SAMP> and sorts the first <SAMP>mid - start</SAMP> values in ascending order. The remaining elements in the range (those in <SAMP>[mid, finish)</SAMP>) are not in any defined order. 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> |
| <A NAME="sec5"><H3>Complexity</H3></A> |
| <P><SAMP>partial_sort()</SAMP> does approximately<SAMP> (finish - start) * log(mid-start) </SAMP>comparisons. This implementation of <SAMP>partial_sort()</SAMP> is implemented using heapsort, which is <SAMP>O(N * log(N))</SAMP> in the worst case. </P> |
| <A NAME="sec6"><H3>Example</H3></A> |
| |
| <UL><PRE>// |
| // partsort.cpp |
| // |
| |
| #include <algorithm> // for partial_sort |
| #include <iostream> // for cout, endl |
| #include <iterator> // for ostream_iterator |
| #include <vector> // for vector |
| |
| |
| |
| int main() |
| { |
| typedef std::vector<int, std::allocator<int> > Vector; |
| |
| typedef std::ostream_iterator<int, char, |
| std::char_traits<char> > |
| Iter; |
| |
| const Vector::value_type a[] = { |
| 17, 3, 5, -4, 1, 12, -10, -1, 14, 7, |
| -6, 8, 15, -11, 2, -2, 18, 4, -3, 0 |
| }; |
| |
| Vector v1 (a + 0, a + sizeof a / sizeof *a); |
| |
| // Output original vector. |
| std::cout << "For the vector: "; |
| std::copy (v1.begin (), v1.end (), Iter (std::cout, " ")); |
| |
| // Partial sort the first seven elements. |
| std::partial_sort (v1.begin (), v1.begin () + 7, |
| v1.end ()); |
| |
| // Output result. |
| std::cout << "\n\nA partial_sort of seven elements " |
| << "gives: \n "; |
| std::copy (v1.begin (), v1.end (), Iter (std::cout, " ")); |
| std::cout << std::endl; |
| |
| // A vector of ten elements. |
| Vector v2 (Vector::size_type (10), 0); |
| |
| // Sort the last ten elements in v1 into v2. |
| std::partial_sort_copy (v1.begin () + 10, v1.end (), |
| v2.begin (), v2.end ()); |
| |
| // Output result. |
| std::cout |
| << "\nA partial_sort_copy of the last ten elements " |
| << "gives: \n "; |
| std::copy (v2.begin (), v2.end (), Iter (std::cout, " ")); |
| |
| std::cout << std::endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| </PRE></UL> |
| <UL><PRE>For the vector: 17 3 5 -4 1 12 -10 -1 14 7 -6 8 15 -11 2 -2 |
| 18 4 -3 0 |
| |
| A partial_sort of seven elements gives: |
| -11 -10 -6 -4 -3 -2 -1 17 14 12 7 8 15 5 3 2 18 4 1 0 |
| |
| A partial_sort_copy of the last ten elements gives: |
| 0 1 2 3 4 5 7 8 15 18 |
| </PRE></UL> |
| <A NAME="sec7"><H3>See Also</H3></A> |
| <P><SAMP><A HREF="sort.html">sort()</A></SAMP>, <SAMP><A HREF="stable-sort.html">stable_sort()</A></SAMP>, <SAMP><A HREF="partial-sort-copy.html">partial_sort_copy()</A></SAMP> </P> |
| <A NAME="sec8"><H3>Standards Conformance</H3></A> |
| <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.1.3</I></P> |
| |
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