partial_sort_copy (STL Samples)

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

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

Remarks

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 nonpredicate version of partial_sort_copy uses operator< for comparisons.

Example

// partial_sort_copy.cpp
// compile with: /EHsc
// Illustrates how to use 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 ;
}

Output

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  }

Requirements

Header: <algorithm>

See Also

Concepts

Standard Template Library Samples