#2428 - Maximum Sum of an Hourglass

Medium • View on LeetCode • View on GitHub

Problem Description

You are given an m x n integer matrix grid.

We define an hourglass as a part of the matrix with the following form.

Return the maximum sum of the elements of an hourglass.

Note that an hourglass cannot be rotated and must be entirely contained within the matrix.

Solution

/**
 * @param {number[][]} grid
 * @return {number}
 */
var maxSum = function(grid) {
  let result = 0;
  const rows = grid.length;
  const cols = grid[0].length;

  for (let i = 0; i <= rows - 3; i++) {
    for (let j = 0; j <= cols - 3; j++) {
      const hourglassSum = grid[i][j] + grid[i][j+1] + grid[i][j+2] + grid[i+1][j+1]
        + grid[i+2][j] + grid[i+2][j+1] + grid[i+2][j+2];
      result = Math.max(result, hourglassSum);
    }
  }

  return result;
};