DiagonalDifference.swift

/* 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
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 2.

*/

func diagonalDifference(arr: [[Int]]) -> Int {
        
    var leftToRight = 0
    var rightToLeft = 0

    for i in 0..<arr.count {
        leftToRight += arr[i][i]
        rightToLeft += arr[i][arr.count-1-i]
    }
    return abs(leftToRight-rightToLeft)
}



print(diagonalDifference(arr: [[1,2,3], [4,5,6], [9,8,9]]))       // 2
print(diagonalDifference(arr: [[11,2,4], [4,5,6], [10,8,-12]]))   // 15