Diagonal Difference

/*
 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
 4 5 6
 9 8 9
 The left-to-right diagonal = . The right to left diagonal = . Their absolute difference is .
 
 Function description
 
 Complete the  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, , the number of rows and columns in the matrix .
 Each of the next  lines describes a row, , and consists of  space-separated integers .
 
 Constraints
 
 Output Format
 
 Print the absolute difference between the sums of the matrix's two diagonals as a single integer.
 
 Sample Input
 
 3
 11 2 4
 4 5 6
 10 8 -12
 Sample Output
 
 15
 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
 */

import UIKit
import Foundation

func diagonalDifference(arr: [[Int]]) -> Int {
    var sumD1 : Int = 0
    var sumD2 = 0
    for i in 0..<arr.count{
        sumD1 = sumD1 + arr[i][i]
        sumD2 = sumD2 + arr[arr.count - i - 1][i]
    }
    print(sumD1)
    return abs(sumD1 - sumD2)
}

diagonalDifference(arr: [[11,2, 4],[4,5, 6],[10, 8, -12]])