Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

 
random_shuffle
 
 - Randomly shuffles elements of a collection.
 
 
 

SYNOPSIS

 
 
#include <algorithm>
template <class RandomAccessIterator>
void random_shuffle (RandomAccessIterator first,

RandomAccessIterator last);

 
template <class RandomAccessIterator,

class RandomNumberGenerator>

void random_shuffle (RandomAccessIterator first,

RandomAccessIterator last,
RandomNumberGenerator& rand);
 
 
 

DESCRIPTION

 
 
The random_shuffle algorithm shuffles the elements in the range [first, last) with uniform distribution. random_shuffle can take a particular random number generating function object rand (where rand takes a positive argument n of distance type of the RandomAccessIterator) and returns a randomly chosen value between 0 and n - 1. 
 
 
 

COMPLEXITY

 
 
In the random_shuffle algorithm, (last - first) -1 swaps are done. 
 
 
 

EXAMPLE

//
// rndshufl.cpp
//

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

using namespace std;
int main()

{

//Initialize a vector with an array of ints

int arr[10] = {1,2,3,4,5,6,7,8,9,10};
vector<int> v(arr, arr+10);

//Print out elements in original (sorted) order

cout << "Elements before random_shuffle: " << endl

<< "     ";

copy(v.begin(),v.end(),

ostream_iterator<int,char>(cout," "));

cout << endl << endl;

//Mix them up with random_shuffle
random_shuffle(v.begin(), v.end());
//Print out the mixed up elements

cout << "Elements after random_shuffle: " << endl << "     ";
copy(v.begin(),v.end(),

ostream_iterator<int,char>(cout," "));

cout << endl;

return 0;

}
 

Program Output
 
 
 

 
Elements before random_shuffle:

1 2 3 4 5 6 7 8 9 10

Elements after random_shuffle:

7 9 10 3 2 5 4 8 1 6
 
 
 

WARNINGS

 
 
If your compiler does not support default template parameters, you always need to supply the Allocator template argument. For instance, you need to write:
 
vector<int, allocator<int> >
 
instead of:
 
vector<int>
 
If your compiler does not support namespaces, then you do not need the using declaration for std. 
 

Rogue Wave Software  —  Last change: 02 Apr 1998