Leetcode 317. Shortest Distance from All Buildings

Given a grid with buildings (1), empty land (0), and obstacles (2), find an empty cell that minimizes the sum of shortest (Manhattan) path distances from all buildings while avoiding obstacles; return that minimum sum or -1 if no empty cell is reachable from every building. This problem primarily requires repeated BFS distance accumulation and reachability checks from each building to identify the globally optimal empty location.