Leetcode 1274. Number of Ships in a Rectangle

Given a black-box API hasShips(topRight, bottomLeft) that returns whether at least one ship (point at integer coordinates) lies inside an axis-aligned rectangle, compute the exact number of ships in a target rectangle by recursively subdividing the region (quadtree/divide-and-conquer), pruning empty subrectangles and stopping when a region reduces to a single point.