Why am I getting an error for this hour glass problem with Java?

April 7, 2022

I am supposed to return the max hourglass sum. I am looping through the 2D array list to get the answer however I am getting 14 instead of 19 which is the correct answer. The code is given below:

public static int hourglassSum(List<List<Integer>> arr) {
    // Write your code here
    
    int hour_glass_sum = 0;
    
    int max = Integer.MIN_VALUE;
    
    for(int i=0; i < 4; i++) {
        //It loops through the entire list
        
        for(int j =0; j < 4; j++) {
            hour_glass_sum  = arr.get(i).get(j) + arr.get(i).get(j+1) + arr.get(i).get(j+2)+arr.get(i+1).get(j+1)+arr.get(i+2).get(j)+arr.get(i+2).get(j+1)+arr.get(i+2).get(j+2); 
        } 
        
        max = Math.max(max, hour_glass_sum);
    }
    
    return max;

    }

}


1 1 1 0 0 0
0 1 0 0 0 0
1 1 1 0 0 0
0 0 2 4 4 0
0 0 0 2 0 0
0 0 1 2 4 0

Expected Output: 19
My Output: 14

Can anyone tell me where am I making the error kindly?

>Solution :

You apply Math.max to the last index of j only

Change:

    for(int j =0; j < 4; j++) {
        hour_glass_sum  = arr.get(i).get(j) + arr.get(i).get(j+1) + arr.get(i).get(j+2)+arr.get(i+1).get(j+1)+arr.get(i+2).get(j)+arr.get(i+2).get(j+1)+arr.get(i+2).get(j+2); 
    } 
        
    max = Math.max(max, hour_glass_sum);

to :

    for(int j =0; j < 4; j++) {
        hour_glass_sum  = arr.get(i).get(j) + arr.get(i).get(j+1) + arr.get(i).get(j+2)+arr.get(i+1).get(j+1)+arr.get(i+2).get(j)+arr.get(i+2).get(j+1)+arr.get(i+2).get(j+2); 
        max = Math.max(max, hour_glass_sum);
    }