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 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) {
        let output = "";
        for (let j = 0; j < N; ++j)
            output += array[i][j] + " "
        console.log(output.trim());
    }

}

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

// This code is contributed by subham348.

6 5 4
1 2 3
9 8 7

Complexity Analysis:

• 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!