#636 · #2290 · Minimum Obstacle Removal to Reach Corner(到达角落需要移除障碍物的最小数目)

You are given an m x n grid where 0 is empty and 1 is an obstacle. You may move in the four cardinal directions; moving into an obstacle removes it (cost 1), and moving into an empty cell is free. Return the minimum obstacles removed to reach the bottom-right from the top-left. Constraints: 1 <= m, n <= 10^5, 2 <= m * n <= 10^5.