Diagonal Difference HackerRank solution

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.

in c++

int diagonalDifference(vector<vector<int>> arr,int n) { int lft=0,rit=0; for(int i=0;i<n;i++){ lft += arr[i][i]; rit += arr[(n-i)][(n-i)]; } return abs(rit-lft); }