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Predicate Version of partial_sort_copy 

Illustrates how to use the predicate version of the partial_sort_copy Standard Template Library (STL) function in Visual C++.


template<class InputIterator, RandomAccessIterator, class Compare> inline
   RandomAccessIterator partial_sort(
      InputIterator First1,
       InputIterator Last1,
      RandomAccessIterator First2,
      RandomAccessIterator Last2,
      Compare Compare
   )

NoteNote

The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

The partial_sort_copy algorithm sorts the smallest n elements, where n = min((Last1 - First1), (Last2 - First2)), of the sequence [First1, Last1), and copies the results to the sequence [First2, First2 + n]. The predicate version of partial_sort_copy uses the compare function for comparisons.

// partial_sort_copyP.cpp
// compile with: /EHsc
// Illustrates how to use the predicate version
// of the partial_sort_copy function.
//
// Functions:
//    partial_sort_copy : Sort the smallest N elements in a sequence
//                        and copy the resulting sequence
//                        to another sequence.
//////////////////////////////////////////////////////////////////////

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>

using namespace std ;

int main()
{
    const int VECTOR_SIZE = 8 ;

    // Define a template class vector of int
    typedef vector<int> IntVector;

    //Define an iterator for template class vector of strings
    typedef IntVector::iterator IntVectorIt;

    IntVector Numbers(VECTOR_SIZE);
    IntVector Result(4);

    IntVectorIt start, end, it;

    // Initialize vector Numbers
    Numbers[0] = 4;
    Numbers[1] = 10;
    Numbers[2] = 70;
    Numbers[3] = 30;
    Numbers[4] = 10;
    Numbers[5] = 69;
    Numbers[6] = 96;
    Numbers[7] = 7;

    start = Numbers.begin();    // location of first
                                // element of Numbers

    end = Numbers.end();        // one past the location
                                // last element of Numbers

    cout << "Before calling partial_sort_copy\n" << endl;

    // print content of Numbers
    cout << "Numbers { ";
    for(it = start; it != end; it++)
        cout << *it << " ";
    cout << " }\n" << endl;

    // sort the smallest 4 elements in the Numbers
    // and copy the results in Result
    partial_sort_copy(start, end, Result.begin(),Result.end());

    cout << "After calling partial_sort_copy\n" << endl;

    cout << "Numbers { ";
    for(it = start; it != end; it++)
        cout << *it << " ";
    cout << " }\n" << endl;

    cout << "Result { " ;
    for(it = Result.begin(); it != Result.end(); it++)
        cout << *it << " ";
    cout << " }\n" << endl;
}

Before calling partial_sort_copy

Numbers { 4 10 70 30 10 69 96 7  }

After calling partial_sort_copy

Numbers { 4 10 70 30 10 69 96 7  }

Result { 4 7 10 10  }

Header: <algorithm>

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