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 generat-
ing function object rand (where rand takes a positive argu-
ment 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 parame-
ters, you always need to supply the Allocator template argu-
ment. 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.