hackerrank - interview kit - 2d arrays

hourglassSum.cpp

/* 
Given a  2D Array, :

1 1 1 0 0 0
0 1 0 0 0 0
1 1 1 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
We define an hourglass in  to be a subset of values with indices falling in this pattern in 's graphical representation:

a b c
  d
e f g
There are  hourglasses in , and an hourglass sum is the sum of an hourglass' values. Calculate the hourglass sum for every hourglass in , then print the maximum hourglass sum.
*/

int hourglassSum(vector<vector<int>> arr) {

    int max =numeric_limits<int>::min();
    for(int i=0; i<arr.size()-2;++i){
        for(int j=0; j< arr[i].size()-2; ++j){
            int sumUpSide = arr[i][j]+arr[i][j+1]+arr[i][j+2];
            int sumMiddle = arr[i+1][j+1];
            int sumDownSide = arr[i+2][j]+arr[i+2][j+1]+arr[i+2][j+2];
            int sum = sumUpSide + sumMiddle + sumDownSide;
            if(sum>max){
                max=sum;
            }
        }
    }
    return max;
}