std::random_shuffle, std::shuffle

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Defined in header <algorithm>

template< class RandomAccessIterator >
void random_shuffle( RandomAccessIterator first, RandomAccessIterator last );
(1)
template< class RandomAccessIterator, class RandomNumberGenerator >

void random_shuffle( RandomAccessIterator first, RandomAccessIterator last,
                     RandomNumberGenerator& r );
template< class RandomAccessIterator, class RandomNumberGenerator >
void random_shuffle( RandomAccessIterator first, RandomAccessIterator last,

                     RandomNumberGenerator&& r );
(2) (pre-C++11 version)


(C++11 version)

template< class RandomAccessIterator, class UniformRandomNumberGenerator >

void shuffle( RandomAccessIterator first, RandomAccessIterator last,

              UniformRandomNumberGenerator&& g );
(3) (C++11 feature)

Reorders the elements in the given range [first, last) such that each possible permutation of those elements has equal probability of appearance.

1) The random number generator is implementation-defined, the rand function may be used.

2) The random number generator is the function object r.

3) The random number generator is the function object g.

Contents

[edit] Parameters

first, last - the range of elements to shuffle randomly
r - function object returning a randomly chosen value of type iterator_traits<RandomAccessIterator>::difference_type in the interval [0,n) if invoked as r(n)
g - function object returning a randomly chosen value of type UniformRandomNumberGenerator::result_type in the interval [g.min(), g.max()] if invoked as g() (intended to be used with uniform random number generators from the standard library)

[edit] Return value

(none)

[edit] Complexity

linear in the distance between first and last

[edit] Equivalent function

[edit] Example

The following code randomly shuffles the integers 1..10

#include <random>
#include <algorithm>
#include <iterator>
#include <iostream>
 
int main()
{
    std::vector<int> v = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
 
    std::random_device rd;
    std::mt19937 g(rd());
 
    std::shuffle(v.begin(), v.end(), g);
 
    copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
}

Output:

8 6 10 4 2 3 7 1 9 5

[edit] See also

next_permutation
generates the next greater lexicographic permutation of a range of elements
(function template)
prev_permutation
generates the next smaller lexicographic permutation of a range of elements
(function template)