Algorithms — Diagonal Difference Solution using JavaScript: HackerRank

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

•Published on2012-12-01

For example, the square matrix is shown below:

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

**. — 100 ≤ arr[i][j] ≤ 100

Output Format

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

Sample Input

11 2 4
4 5 6
10 8 -12

Sample Output

Explanation

The primary diagonal is:

11
   5
     -12

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

The secondary diagonal is:

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

Using JavaScript:

**function** diagonalDifference(arr) {

**    var** n = arr.length;
    **var** d1 = 0;
    **var** d2 = 0;

**  for**(**var** i=0; i<n; i++){

**     for**(**var** j=0; j<n; j++){
       *// finding the sum of primary diagonal*

**         if**(i === j) {
           d1 += arr[i][j];
         }
       *// finding the sum of secondary diagonal*

**         if**(i + j === n - 1){
            d2 += arr[i][j];
         }

      }

  }
  **return** Math.abs(d1 - d2);
}