The kind of problem that looks straightforward until you're actually writing the boundary conditions.
Clarify the problem and edge cases, then propose a layer-by-layer traversal using four boundaries (top, bottom, left, right). Walk through the algorithm with a small example, analyze time and space complexity, and discuss potential optimizations or alternative approaches.
Pro tip: Mention that you can avoid explicit boundary checks by using a direction array and a visited matrix, but note the trade-off in space. Also, emphasize the importance of handling non-square matrices and empty input gracefully.
Ask clarifying questions: Can the matrix be empty? Are there constraints on m and n? Should the output be a list or array? Confirm the expected order (clockwise spiral starting from top-left).
Explain the boundary-based traversal: maintain four pointers (top, bottom, left, right) and traverse the outer layer, then shrink the boundaries and repeat until all elements are visited.
Use a small matrix (e.g., 3x3 or 3x4) to demonstrate the traversal step by step, showing how boundaries update and when to stop.
State that time complexity is O(m*n) since each element is visited once, and space complexity is O(1) extra space (excluding the output array).
Mention edge cases: empty matrix, single row/column, non-square matrices. Briefly discuss alternative approaches like simulation with direction changes and visited matrix, noting its O(m*n) space overhead.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.