2D Prefix Sum
Extend the Prefix Sum technique to two dimensions — efficiently answer rectangular range sum queries on a 2D grid in O(1) after O(m×n) preprocessing. Includes intuition, dry runs, and multi-language implementations.
Extend the Prefix Sum technique to two dimensions — efficiently answer rectangular range sum queries on a 2D grid in O(1) after O(m×n) preprocessing. Includes intuition, dry runs, and multi-language implementations.