Clarify the problem and edge cases, then propose a BFS solution using a queue to process nodes level by level. Explain how to track level boundaries and collect values into sublists, and analyze time and space complexity.
Pro tip: Mention that BFS is ideal for level-order traversal, but also discuss how DFS with level tracking can achieve the same result, showing versatility. Emphasize the importance of handling edge cases like an empty tree and skewed trees.
Confirm the output format (list of lists), input constraints, and edge cases such as empty tree, single node, and skewed trees.
Explain that BFS naturally processes nodes level by level. Use a queue to store nodes and process each level by iterating over the current queue size.
For each level, record the number of nodes (queue size), dequeue that many nodes, collect their values, and enqueue their children.
State that time complexity is O(N) where N is the number of nodes, and space complexity is O(W) where W is the maximum width of the tree.
Mention DFS with level parameter as an alternative, and discuss potential optimizations like using a deque or handling large trees.
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