My first instinct was DFS and just tracking the first node at each depth, which works fine.
Use a level-order traversal (BFS) with a queue, and for each level, record the first node encountered. Alternatively, use DFS with a depth parameter, recording the first node seen at each depth. Clearly explain the chosen approach, its time and space complexity, and handle edge cases like an empty tree.
Pro tip: Mention that the left view can be obtained by modifying a standard BFS to only capture the first node of each level, and note that DFS with a depth check is more space-efficient for skewed trees. This shows you understand trade-offs and can adapt to constraints.
Confirm that the left view includes the leftmost node at each level, and discuss handling of an empty tree or single-node tree.
Decide between BFS (level-order traversal) and DFS (pre-order with depth tracking), and justify your choice based on time/space complexity or tree shape.
Describe step-by-step how to implement the chosen approach, including data structures (queue or recursion stack) and how to identify the first node at each level.
State the time complexity (O(n) for both) and space complexity (O(w) for BFS where w is max width, O(h) for DFS where h is height).
Walk through a small example tree to verify the algorithm produces the correct left view, and mention potential pitfalls like null children.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.