Diagonal Difference

Given a square matrix, calculate the absolute difference between the sums of its diagonals.

For example, the square matrix is shown below:

1
2
3

1 2 3
4 5 6
9 8 9

The left-to-right diagonal = 1 + 5 + 9 = 15. The right to left diagonal = 3 + 5 + 9 = 17. Their absolute difference is |15 - 17| = 2.

Function description

Complete the diagonalDifference function in the editor below. It must return an integer representing the absolute diagonal difference.

diagonalDifference takes the following parameter:

• arr: an array of integers .

Input Format

The first line contains a single integer, n, the number of rows and columns in the matrix arr. Each of the next n lines describes a row, arr[i], and consists of n space-separated integers arr[i][j].

Constraints

Output Format

Print the absolute difference between the sums of the matrix’s two diagonals as a single integer.

Sample Input

1
2
3
4

3
11 2 4
4 5 6
10 8 -12

Sample Output

1

15

Explanation

The primary diagonal is:

1
2
3

11
   5
     -12

Sum across the primary diagonal: 11 + 5 - 12 = 4

The secondary diagonal is:

1
2
3

     4
   5
10

Sum across the secondary diagonal: 4 + 5 + 10 = 19
Difference: |4 - 19| = 15

• Note: |x| is the absolute value of x

Solution

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2
3
4
5
6
7

function diagonalDifference(arr) {
    // Write your code here
    return Math.abs(arr.reduce((target, item, index) => {
        let length = item.length - 1;
        return target + item[index] - item[length - index]
    }, 0));
}