题解:
class Solution {
public int diagonalSum(int[][] mat) {
int n = mat.length;
int sum = 0;
for(int i = 0;i < n;i++){
sum += mat[i][i];
sum += mat[i][n-i-1];
}
if(n % 2 != 0){
sum -= mat[n/2][n/2];
}
return sum;
}
}