RajSharma - 5 months ago 18

Java Question

I am working on a problem where I've to print the largest sum among all the hourglasses in the array. You can find the details about the problem here-

**What I tried-**

`public class Solution {`

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int arr[][] = new int[6][6];

for(int arr_i=0; arr_i < 6; arr_i++){

for(int arr_j=0; arr_j < 6; arr_j++){

arr[arr_i][arr_j] = in.nextInt();

}

}

int sum = 0;

int tmp_sum = 0;

for (int arr_i = 0; arr_i < 4; arr_i++) {

for (int arr_j = 0; arr_j < 4; arr_j++) {

if (arr[arr_i][arr_j] > 0) {

sum = sum + (arr[arr_i][arr_j]) + (arr[arr_i][arr_j + 1]) + (arr[arr_i][arr_j + 2]);

sum = sum + (arr[arr_i + 1][arr_j + 1]);

sum = sum + (arr[arr_i + 2][arr_j]) + (arr[arr_i + 2][arr_j + 1]) + (arr[arr_i + 2][arr_j + 2]);

if (tmp_sum < sum) {

tmp_sum = sum;

}

sum = 0;

}

}

}

System.out.println(tmp_sum);

}

}

`1 1 1 0 0 0`

0 1 0 0 0 0

1 1 1 0 0 0

0 9 2 -4 -4 0

0 0 0 -2 0 0

0 0 -1 -2 -4 0

`12`

`13`

I don't know where I am doing wrong. I cannot understand why the expected output is 13. According to the description given in the problem it should be 10. Is this a wrong question or my understanding about this is wrong?

Answer

Remove the `if (arr[arr_i][arr_j] > 0)`

statement. It prevents finding the answer at row 1, column 0, because that cell is `0`

.

Comments for other improvements to your code:

What if the best hourglass sum is

`-4`

? You should initialize`tmp_sum`

to`Integer.MIN_VALUE`

. And name it`maxSum`

, to better describe it's purpose.You shouldn't define

`sum`

outside the loop. Declare it when it is first assigned, then you don't have to reset it to`0`

afterwards.Your iterators should be just

`i`

and`j`

. Those are standard names for integer iterators, and keeps code ... cleaner.

If you prefer longer names, use`row`

and`col`

, since that is what they represent.You don't need parenthesis around the array lookups.

For clarity, I formatted the code below to show the hourglass shape in the array lookups.

```
Scanner in = new Scanner(System.in);
int arr[][] = new int[6][6];
for (int i = 0; i < 6; i++){
for (int j = 0; j < 6; j++){
arr[i][j] = in.nextInt();
}
}
int maxSum = Integer.MIN_VALUE;
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
int sum = arr[i ][j] + arr[i ][j + 1] + arr[i ][j + 2]
+ arr[i + 1][j + 1]
+ arr[i + 2][j] + arr[i + 2][j + 1] + arr[i + 2][j + 2];
if (maxSum < sum) {
maxSum = sum;
}
}
}
System.out.println(maxSum);
```