Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.

NAME

  partial_sort_copy  - Templated algorithm for sorting collections of
  entities.

SYNOPSIS

  #include <algorithm>

  template <class InputIterator,
           class RandomAccessIterator>
  void partial_sort_copy (InputIterator first,
                          InputIterator last,
                          RandomAccessIterator result_first,
                          RandomAccessIterator result_last);
  template <class InputIterator,
           class RandomAccessIterator,
           class Compare>
  void partial_sort_copy (InputIterator first,
                          InputIterator last,
                          RandomAccessIterator result_first,
                          RandomAccessIterator result_last,
                          Compare comp);

DESCRIPTION

  The partial_sort_copy algorithm places the smaller of last - first and
  result_last - result_first  sorted elements from the range [first, last)
  into the range beginning at result_first. (i.e., the range: [result_first,
  result_first+min(last - first, result_last - result_first)).  Basically,
  the effect is as if the range [first,last) were placed in a temporary
  buffer, sorted and then as many elements as possible were copied into the
  range [result_first, result_last).

  The first version of the algorithm uses less than (operator<) as the
  comparison operator  for the sort.  The second version uses the comparison
  function comp.

COMPLEXITY

  partial_sort_copy does approximately (last-first) * log(min(last-first,
  result_last-result_first)) comparisons.

EXAMPLE

  //
  // partsort.cpp
  // #include <vector>
   #include <algorithm>
   #include <iostream.h>
  int main()
   {
    int d1[20] = {17, 3,  5,  -4, 1, 12, -10, -1, 14, 7,
                   -6, 8, 15, -11, 2, -2,  18,  4, -3, 0};
     //
     // Set up a vector.
     //
    vector<int> v1(d1+0, d1+20);
     //
     // Output original vector.
     //
    cout << "For the vector: ";
    copy(v1.begin(), v1.end(), ostream_iterator<int>(cout," "));
     //
     // Partial sort the first seven elements.
     //
    partial_sort(v1.begin(), v1.begin()+7, v1.end());
     //
     // Output result.
     //
    cout << endl << endl << "A partial_sort of 7 elements gives: "
          << endl << "     ";
    copy(v1.begin(), v1.end(),
         ostream_iterator<int,char>(cout," "));
    cout << endl;
     //
     // A vector of ten elements.
     //
    vector<int> v2(10, 0);
     //
     // Sort the last ten elements in v1 into v2.
     //
     partial_sort_copy(v1.begin()+10, v1.end(), v2.begin(),
                          v2.end());
     //
     // Output result.
     //
    cout << endl << "A partial_sort_copy of the last ten elements
                        gives: " << endl << "     ";
    copy(v2.begin(), v2.end(),
         ostream_iterator<int,char>(cout," "));
    cout << endl;
    return 0;
   }
  Output :
  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

WARNING

  If your compiler does not support default template parameters, then you
  need to always provide the Allocator template argument.  For instance, you
  will need to write :

  vector<int, allocator<int> >

  instead of :

  vector<int>

SEE ALSO

  sort_ stable_sort, partial_sort

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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