grid[r][c] is the ore content of one cell of a mining map. A survey block is exactly h rows tall and w columns wide and must lie fully inside the map. Return the largest total ore content of any such block. It is guaranteed that h <= rows and w <= cols.
Examples
Input: grid = [[1, -2, 3], [4, 5, -6], [-7, 8, 9]], h = 2, w = 2
Output: 16
Explanation: the bottom-right block 5 + (-6) + 8 + 9 = 16 beats the other three blocks (8, 0, 10).
Input: grid = [[2, 3]], h = 1, w = 1
Output: 3
Constraints
1 <= rows, cols <= 300,1 <= h <= rows,1 <= w <= cols-1000 <= grid[r][c] <= 1000- Target complexity: O(rows * cols). Summing every block cell by cell is too slow for the largest tests.
Goals
- Reuse a summed-area table to score every candidate block in O(1)
- Enumerate all top-left corners without running off the grid