Given a grid of integers grid and an integer k, return the largest possible sum of a k x k
sub-grid (a block of k consecutive rows and k consecutive columns).
Examples
Input: grid = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]], k = 2
Output: 28
Explanation: the bottom-right block 5 + 6 + 8 + 9 is the largest.
Input: grid = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]], k = 3
Output: 45
Input: grid = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]], k = 1
Output: 9
Constraints
1 <= k <= min(rows, cols) <= 60,-1000 <= grid[r][c] <= 1000
Goals
- Enumerate all k x k sub-grids of a larger grid
- Sum a rectangular region and track the best