Maximum Rectangle Sum — Solution & Editorial

Back to the Problem

Fix a top and bottom row pair, collapse the columns between them into a 1-D array of column sums, and run Kadane's maximum-subarray on it. O(N²M) total.

Complexity: O(N² M)

Watch out: All-negative grids: never clamp Kadane at 0 — the answer is the least-negative single cell.