Matrix Diagonal Sum

class Solution {
    public int diagonalSum(int[][] mat) {
        int toMinus = 0;
        if(mat.length % 2 == 1){
            toMinus = mat[mat.length/2][mat.length/2];
        }
        int left = 0;
        int right = mat.length-1;
        int sum = 0;
        for(int i = 0; i<mat.length; i++){
            sum += mat[i][left++];
            sum += mat[i][right--];
        }
        //System.out.println(toMinus);
        return sum - toMinus;
    }
}