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random_shuffle
Brings the elements into a random order
Definition
The random_shuffle() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.Interface
#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 );Parameters:
| Parameter | Description |
|---|---|
| first | A random-access iterator addressing the position of the first element in the range to be rearranged |
| last | A random-access iterator addressing the position one past the final element in the range to be rearranged |
| rand | A special function object called a random number generator |
Description
Random_shuffle function reorders the elements of a range by putting them at random places. The first version uses an internal random number generator, and the second uses a Random Number Generator, a special kind of function object, that is explicitly passed as an argument.Complexity
The complexity is linear; performs as many calls to swap as the length of the range[first,last) - 1.Example:
Example - random_shuffle algorithm
Problem
This program illustrates the use of the STL random_shuffle() algorithm (default version) to randomize the order of values in a vector of integers.
Workings
#include <iostream> #include <vector> #include <algorithm> using namespace std; int main() { int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; vector<int> v(a, a+10); cout <<"\nHere are the values in the vector:\n"; for (vector<int>::size_type i=0; i<v.size(); i++) cout <<v.at(i)<<" "; cout << "\nNow we randomize the order of the values."; random_shuffle(v.begin(), v.end()); cout <<"\nHere are the revised contents of the vector:\n"; for (vector<int>::size_type i=0; i<v.size(); i++) cout <<v.at(i)<<" "; return 0; }
Solution
Output:
Here are the values in the vector:
1 2 3 4 5 6 7 8 9 10 Now we randomize the order of the values. Here are the revised contents of the vector:
9 2 10 3 1 6 8 4 5 7
1 2 3 4 5 6 7 8 9 10 Now we randomize the order of the values. Here are the revised contents of the vector:
9 2 10 3 1 6 8 4 5 7
References
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