DOCUMENT:Q158004  05-MAY-2001  [visualc]
TITLE   :STL Sample for the random_shuffle Function
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:
OPER/SYS:
KEYWORDS:_IK

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The information in this article applies to:

 - The Standard C++ Library, included with:
    - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 4.2 
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SUMMARY
=======

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

MORE INFORMATION
================

Required Header
---------------

      <algorithm>

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.

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.

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  }

REFERENCES
==========

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

Additional query words: 4.00 STL random_shuffle

======================================================================
Keywords          : _IK 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : winnt:
Issue type        : kbhowto

=============================================================================

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