Javascript Program to Interchange Diagonals of Matrix

Given a square matrix of order n*n, you have to interchange the elements of both diagonals. 
Examples :

Input : matrix[][] = {1, 2, 3,
                      4, 5, 6,
                      7, 8, 9} 
Output : matrix[][] = {3, 2, 1,
                       4, 5, 6,
                       9, 8, 7} 

Input : matrix[][] = {4,  2,  3,  1,
                      5,  7,  6,  8,
                      9, 11, 10, 12,
                     16, 14, 15, 13} 
Output : matrix[][] = {1,  2,  3,  4,
                       5,  6,  7,  8,
                       9, 10, 11, 12,
                      11, 14, 15, 16}

Explanation : Idea behind interchanging diagonals of a square matrix is simple. Iterate from 0 to n-1 and for each iteration you have to swap a[i][i] and a[i][n-i-1]. 

Javascript

<script>
// Javascript program to interchange
// the diagonals of matrix
let N = 3;

// Function to interchange diagonals
function interchangeDiagonals(array)
{

    // swap elements of diagonal
    for (let i = 0; i < N; ++i)
    if (i != parseInt(N / 2)) {
        let temp = array[i][i];
        array[i][i] = array[i][N - i - 1];
        array[i][N - i - 1] = temp;
    }
    for (let i = 0; i < N; ++i)
    {
    for (let j = 0; j < N; ++j)
            document.write(" " + array[i][j]);
    document.write("<br>");
    }
}

// Driver Code
    let array = [[4, 5, 6],
                    [1, 2, 3],
                    [7, 8, 9]];
    interchangeDiagonals(array);

// This code is contributed by subham348.
</script>

Output:

 6 5 4
 1 2 3
 9 8 7

Time Complexity: O(N*N), as we are using nested loops for traversing the matrix.

Auxiliary Space: O(1), as we are not using any extra space.

Please refer complete article on Program to Interchange Diagonals of Matrix for more details!