Compute shortest path in a 2D grid

Given an `m x n` grid where: - `0` represents an empty cell you can move through - `1` represents a blocked cell you cannot enter - movement is allowed in 4 directions (up, down, left, right) You are also given coordinates `start = (sr, sc)` and `target = (tr, tc)` (both are inside the grid). Return the length of the shortest path (number of moves) from `start` to `target`. If `target` is unreachable, return `-1`. Explain the algorithm you would use and its time/space complexity.