C++ Program to Implement Fisher-Yates Algorithm for Array Shuffling

Fisher-Yates algorithm generates a random permutation of the array elements i.e. it randomly shuffles all the elements of an array. All the permutations for the array are equally likely as the Fisher-Yates algorithm is unbiased.

A program to implement the Fisher-Yates Algorithm for array shuffling in C++ is given as follows −

Example

#include <iostream>
#include <t;stdlib.h>
using namespace std;
int main() {
   int n;
   cout << "Enter the array size: "<<endl;
   cin >> n;

   int arr[n], arr1[n], index_arr[n];
   int index;
   cout << "Enter the array elements: "<<endl;
   for (int i = 0; i < n; i++)
   cin >> arr[i];
   for (int i = 0; i < n; i++)
   index_arr[i] = 0;
   for (int i = 0; i < n; i++) {
      do {
         index = rand() % n;
      }
      while (index_arr[index] != 0);
      index_arr[index] = 1;
      arr1[i] = arr[index];
   }
   cout<<"The shuffled array is: ";

   for (int i = 0; i < n; i++)
   cout << arr1[i] << " ";
   return 0;
}

Output

The output of the above program is as follows

Enter the array size: 10
Enter the array elements: 1 2 3 4 5 6 7 8 9 10
The shuffled array is: 4 7 8 6 3 10 2 1 9 5

In the above program, the size of the array and the array are requested from the user. This is given below −

cout << "Enter the array size: "<<endl;
cin >> n;

int arr[n], arr1[n], index_arr[n];
int index;

cout << "Enter the array elements: "<<endl;

for (int i = 0; i < n; i++)
cin >> arr[i];

After the array is obtained, index_arr[] is initialized to 0. Then the rand() function is used to randomly store the values of arr[] into arr1[]. This is demonstrated by the following code snippet −

for (int i = 0; i < n; i++) {
do {
   index = rand() % n;
}
while (index_arr[index] != 0);
index_arr[index] = 1;
arr1[i] = arr[index];
}

Finally the shuffled array is displayed. This is seen below −

cout<<"The shuffled array is: ";

for (int i = 0; i < n; i++)
cout << arr1[i] << " ";