hourglass.cpp

// C++ program to find maximum sum of hour
// glass in matrix
#include<bits/stdc++.h>
using namespace std;
const int R = 5;
const int C = 5;

// Returns maximum sum of hour glass in ar[][]
int findMaxSum(int mat[R][C])
{
	if (R<3 || C<3){
		cout << "Not possible" << endl;
		exit(0);
	}

	// Here loop runs (R-2)*(C-2) times considering
	// different top left cells of hour glasses.
	int max_sum = INT_MIN;
	for (int i=0; i<R-2; i++)
	{
		for (int j=0; j<C-2; j++)
		{
			// Considering mat[i][j] as top left cell of
			// hour glass.
			int sum = (mat[i][j]+mat[i][j+1]+mat[i][j+2])+
					(mat[i+1][j+1])+
				(mat[i+2][j]+mat[i+2][j+1]+mat[i+2][j+2]);

			// If previous sum is less than current sum then
			// update new sum in max_sum
			max_sum = max(max_sum, sum);
		}
	}
	return max_sum;
}

// Driver code
int main()
{
	int mat[][C] = {{1, 2, 3, 0, 0},
					{0, 0, 0, 0, 0},
					{2, 1, 4, 0, 0},
					{0, 0, 0, 0, 0},
					{1, 1, 0, 1, 0}};
	int res = findMaxSum(mat);
	cout << "Maximum sum of hour glass = "<< res << endl;
	return 0;
}

//Code is modified by anupam603