I jumped straight to BFS without really explaining why, which I think cost me points.
Clarify the problem constraints (grid size, movement allowed, obstacles) and then propose BFS for shortest path in an unweighted grid. Discuss trade-offs between BFS and DFS, and mention optimizations like bidirectional BFS or A* if applicable.
Pro tip: Always start by asking clarifying questions about the grid and movement rules; this shows thoroughness and can reveal if the problem is weighted or has other nuances. Also, mention that BFS guarantees shortest path in unweighted graphs, which is often expected at Meta.
Ask about grid dimensions, movement directions (4 or 8), whether diagonal moves are allowed, and if the grid is static. Confirm that the goal is to find any path, with bonus for shortest.
For shortest path in an unweighted grid, BFS is optimal. For any path, DFS works but may not be shortest. Discuss trade-offs: BFS uses more memory but guarantees shortest path; DFS uses less memory but may be slower for shortest path.
Use a queue to explore level by level, track visited cells to avoid cycles, and store parent pointers to reconstruct the path. Return the path when goal is reached.
Mention bidirectional BFS to reduce search space, or A* with Manhattan distance heuristic if the grid is large. Note that A* is optimal if heuristic is admissible.
Time complexity O(V+E) where V is number of cells and E is edges (up to 4V). Space O(V). Handle edge cases: start equals goal, no path exists, grid with no obstacles.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.