Graph BFS

Given an n x n binary matrix grid, return the length of the shortest clear path from the top-left cell (0, 0) to the bottom-right cell (n - 1, n - 1), or -1 if no such path exists. A clear path visits only cells with value 0 and may move in any of the 8 directions; its length is the number of cells visited.

On an infinite chessboard, a knight begins at (0, 0). A knight moves two squares along one axis and then one square along the perpendicular axis. Given a target square (x, y), return the minimum number of moves needed to reach it.

You have a lock with 4 circular wheels, each with digits 0–9. The lock starts at '0000'. Each move turns one wheel by one slot (e.g., '1' → '2' or '1' → '0'). Given a list of deadends (lock states you must avoid) and a target combination, return the minimum number of moves to reach target, or -1 if impossible.