Number of Islands API Variant

Approach — Precompute Island Sizes with a Membership Set The core challenge is answering "does an island of size k exist?" efficiently when the same grid receives many queries. A naive approach—rescanning the grid for every query—would be prohibitively expensive at O(Q × R × C) for Q queries. We can do much better by separating the work into two phases: a one-time preprocessing scan that discovers all island sizes, and a lightning-fast lookup for each subsequent query. The…