Shortest path in a grid (BFS) with blocked/unblocked cells and updates

Coding: Shortest Path in a Grid (BFS) Given an m x n grid with open cells 0 and blocked cells 1, find the shortest number of steps from start S=(sr, sc) to target T=(tr, tc). You can move in 4 directions (up/down/left/right) and cannot leave the grid. Return the shortest steps, or -1 if unreachable. I/O Input: m n, then m rows of 0/1 grid, then sr sc tr tc. Output: shortest steps or -1. Constraints 1 <= m,n <= 2000 Single run should be about O(mn). Follow-up If cells may be updated from blocked (1) to open (0) dynamically (possibly many updates), how would you optimize for repeated shortest-path queries? Discuss trade-offs between rerunning BFS and incremental/dynamic approaches. Example Input 3 3 0 0 0 1 1 0 0 0 0 0 0 2 2 Output 4