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STL Sample for the Predicate Version of partial_sort Function

Retired KB ArticleThis article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.
Article ID:158002
Last Review:December 10, 2003
Revision:2.0
This article was previously published under Q158002
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SUMMARY

The sample code below illustrates how to use the predicate version of partial_sort STL function in Visual C++.

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MORE INFORMATION

Required Header

   <algorithm>
				


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Prototype

   template<class RandomAccessIterator, class Compare> inline
   void partial_sort(RandomAccessIterator first,
                     RandomAccessIterator middle,
                     RandomAccessIterator last,
                     Compare compare)
				
NOTE: The class/parameter names in the prototype do not match the original version in the header file. Some have been modified to improve readability.

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Description

The partial_sort algorithm sorts the smallest N elements, where N = middle - first of the sequence [first, last). The remaining elements end up in the range [middle..last) in an undefined order.

The predicate version of partial_sort uses the compare function for comparisons.

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Sample Code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: /GX
// 
// partial_sort.cpp : Illustrates how to use the predicate version
//                    of the partial_sort function.
// 
// Functions:
// 
//    partial_sort : Sort the smallest N elements in a sequence.
// 
// Written by Kalindi Sanghrajka
// of Microsoft Product Support Services,
// Software Core Developer Support.
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
////////////////////////////////////////////////////////////////////// 

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

#include <iostream>
#include <algorithm>
#include <functional>
#include <vector><BR/>
using namespace std;

void main()
{
    const int VECTOR_SIZE = 8 ;

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

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

    IntVector Numbers(VECTOR_SIZE) ;

    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\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 sequence
    partial_sort(start, start+4, end, less<int>()) ;

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

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

Program Output is:

Before calling partial_sort

Numbers { 4 10 70 30 10 69 96 7  }

After calling partial_sort

Numbers { 4 7 10 10 70 69 96 30  }
				

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REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.

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APPLIES TO
The Standard C++ Library, when used with:
  Microsoft Visual C++ 4.2 Professional Edition
  Microsoft Visual C++ 4.2 Enterprise Edition
  Microsoft Visual C++ 5.0 Learning Edition

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Keywords: 
kbcode kbhowto KB158002

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