[Solved] HourGlass with Largest sum in 2D Array in Python and Java

First of all understand the Hourglass. It is shaped as shown in the below image.

There can be multiple hourglass in the 2D array (matrix).

Problem Statement: Write a Python program to find the HourGlass with Largest sum in 2D Array in Python.

Explanation: Solving this problem includes finding all the hourglass and calculating the sum of every hourglass.

This is a coding challenge question. You can solve it in any programming language.

Python Program:

Let’s solve it in Python programming.

Prerequisite:

• Python Programming
• for loop in Python

Code:

arr =[
    [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]]


#This function will return the sum of the hourglass
def sum_hg(x, y):
    sum = arr[x][y] + arr[x][y+1] +arr[x][y+2]
    sum = sum + arr[x+1][y+1]
    sum = sum + arr[x+2][y]+arr[x+2][y+1]+arr[x+2][y+2]
    return sum

size = len(arr)
sum = -63

for x in range(0, (size-2):
    for y in range(0, (size-2):
        k = sum_hg(x, y)
        if k > sum:
            sum = k

print("The largest sum of the HourGlass is ", sum)

Output:

The largest sum of the HourGlass is 19.

Java Program:

Now let’s try to solve this problem in Java programming.

Prerequisite:

• Basic Java Programming
• Flow Control Statement in Java

Java Code:

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class HG_Class {
    public static void main(String[] args) {
        int[][] arr = {{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}};

        int sum=-63;

        for(int p=5; p>=2; p--) {
            for(int q=5; q>=2; q--){

                int  sum_hg = arr[p][q]+arr[p][q-1]+arr[p][q-2];
                sum_hg += arr[p-1][q-1];
                sum_hg += arr[p-2][q]+arr[p-2][q-1]+arr[p-2][q-2];

                if(sum_hg>sum) sum=sum_hg;
            }
        }
        System.out.println("Largest sum of the HourGlass is "+ sum);
    }
}

Output:

Largest sum of the HourGlass is 19

This is how you can find the hourglass with largest sum in 2D array. This question was asked in the HackerRank test. The level of the question is low.