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STL Sample for the random_shuffle 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:158004
Last Review:June 23, 2005
Revision:2.1
This article was previously published under Q158004
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SUMMARY

The sample code below illustrates how to use the random_shuffle STL function in Visual C++.

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MORE INFORMATION

Required Header

   <algorithm>
				

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Prototype

   template<class RandomAccessIterator> inline
   void random_shuffle(RandomAccessIterator first,
                    RandomAccessIterator last)
				
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 random_shuffle algorithm shuffles the elements of a sequence [first..last) in a random order.

The non-predicate version uses an internal random-number generator to generate the indices of the elements to swap.

The non-predicate version of random_shuffle uses operator= to perform swaps.

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Sample Code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: /GX
// 
// random_shuffle.cpp : Illustrates how to use the random_shuffle
//                      function.
// 
// Functions:
// 
//     random_shuffle : Shuffle the elements in a random order.
// 
// 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>
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] = 100;

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

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

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

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

    // shuffle the elements in a random order
    random_shuffle(start, end) ;

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

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


Program Output is:

Before calling random_shuffle

Numbers { 4 10 70 30 10 69 96 100  }

After calling random_shuffle

Numbers { 10 30 4 70 96 100 69 10  }
				

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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 KB158004

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