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                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.


NAME
     partial_sort_copy

      - Templatized algorithm for sorting  collections  of  enti-
     ties.



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  (in  other  words,  the  range: [result_first,
     result_first+min(last - first, result_last - result_first)).
     The  effect is as if the range [first,last) were placed in a
     temporary buffer, sorted, and then as many elements as  pos-
     sible copied into the range [result_first, result_last).

     The first version of the algorithm uses  less  than  (opera-
     tor<)  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>
     using namespace std;
     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(),<br>                     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;
      }

     Program 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



WARNINGS
     If your compiler does not support default  template  parame-
     ters, then you need to always include the Allocator template
     argument. For instance, you need to write:

     vector<int, allocator<int> >

     instead of:

     vector<int>

     If your compiler does not support namespaces,  then  you  do
     not need the using declaration for std.



SEE ALSO
     sort, stable_sort, partial_sort

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