How to Shuffle an array in C++

By Md. Suhail Arif

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In this tutorial, we will solve how to shuffle a given array in C++ which is entered by the user. The size of the array and elements of the array we will take input from the user. We will create a function to shuffle the array of a given size which would take the array and array size as arguments. So, let’s see how to create the function.

Algorithm to create the shuffle function

First, we will initialize stand() with NULL
Then, we will traverse array from the back i.e. n-1
Now, we will assign j with the random array index.
Finally, swap the i^th array element with the j^th element which will shuffle the elements randomly

void shuffle (int arr[], int n) 
{
  
srand (time (NULL));
  
for (int i = n - 1; i > 0; i--)
    {
  
int j = rand () % i;
      
arr[i] = arr[i] + arr[j];      
arr[j] = arr[i] - arr[j];
arr[i] = arr[i] - arr[j];

} 
}

Now, in the main function, we take input from the user.
First, we will input the array size and then the array elements and then we call the shuffle() function
At last print the array which is now shuffled. So, the whole code would look like as given below.

C++ Program to Shuffle an array

#include<iostream>

using namespace std;

void shuffle (int arr[], int n) 
{
srand (time (NULL));
  
for (int i = n - 1; i > 0; i--)
{
      
int j = rand () % i;
      
arr[i] = arr[i] + arr[j];
arr[j] = arr[i] - arr[j];
arr[i] = arr[i] - arr[j];

} 
} 
 
int main () 
{
int arr[20], n, i;
  
cout << "Enter the size of array(max. 20): ";
cin >> n;
  
cout << "Enter the element of array :\n";
  
for (i = 0; i < n; i++)
cin >> arr[i];
  
shuffle (arr, n);
  
cout << "\nshuffled array:";
  
for (i = 0; i < n; i++)
cout << " " << arr[i];
  
return 0;

}

Output:

Enter the size of array(max. 20): 5 
Enter the element of array :
1
2
3
4
5

shuffled array: 4 3 1 5 2

Note: In the given program to shuffle a given array in C++, it gives always different output for the same input.

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