Shuffle a given array | GeeksforGeeks

Given an array, write a program to generate a random permutation of array elements.

Key point: from end to head

To shuffle an array a of n elements (indices 0..n-1):
  for i from n - 1 downto 1 do
       j = random integer with 0 <= j <= i
       exchange a[j] and a[i]

void randomize ( int arr[], int n )

{

    // Use a different seed value so that we don't get same

    // result each time we run this program

    srand ( time(NULL) );

 

    // Start from the last element and swap one by one. We don't

    // need to run for the first element that's why i > 0

    for (int i = n-1; i > 0; i--)

    {

        // Pick a random index from 0 to i

        int j = rand() % (i+1);

 

        // Swap arr[i] with the element at random index

        swap(&arr[i], &arr[j]);

    }

}

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