I spent weeks grinding hard problems and they gave me this.
Start by clarifying the problem and constraints, then present both recursive and iterative solutions, discussing trade-offs. Emphasize clean code, edge cases, and complexity analysis.
Pro tip: At Google, interviewers value candidates who proactively discuss trade-offs and edge cases without being prompted. Mention how you would test the solution and handle large trees to demonstrate production readiness.
Ask about input format, tree node structure, and expected output (e.g., list of values). Confirm if recursion is allowed or if iterative is preferred.
Describe recursive and iterative (stack-based) methods. Mention Morris traversal for O(1) space if applicable.
Write clean code for the chosen approach, handling null root and using appropriate data structures.
State time and space complexity for each approach, noting recursion stack vs explicit stack.
Walk through examples including empty tree, single node, skewed tree, and balanced tree. Mention potential optimizations.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.