HackerRank_Diagonal Difference

Problem

https://www.hackerrank.com/challenges/diagonal-difference/problem?isFullScreen=true&h_r=next-challenge&h_v=zen

Approach

So absolute difference can be calculated like this sum(left to right) - sum(right to left). I was thinking maybe I can calculate both sides at the same time. But I just found easier way by doing loop two times.

 

Solution

function diagonalDifference(arr) {

  const length = arr[0].length;
  
  let result = 0;
  
  // add from left top to right bottom
  for(let i = 0; i < length; i++) {
    result += arr[i][i];
  }
  
  // deduct from right top to left bottom
  for(let j = 0; j < length; j++) {
    result -= arr[j][length-1-j];
  }
  
  // return absolute number
  return Math.abs(result);
  
}