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Bytedance·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Bytedance software engineer round, came across a binary tree inorder traversal problem. Pretty standard stuff but still worth noting it showed up.

Questions Asked (1)

Q1

Implement binary tree inorder traversal.

Algorithms & Data Structures
Author's notes

Classic problem, you'd think it's easy until you try to do the iterative version on the spot with someone watching.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem and constraints, then present both recursive and iterative solutions, explaining the trade-offs. Emphasize the iterative approach using an explicit stack, as it demonstrates deeper understanding and avoids recursion depth issues.

Pro tip: Mention Morris traversal as an O(1) space solution, but note its trade-off of temporarily modifying the tree. This shows you know advanced techniques and can discuss trade-offs.

1. Clarify requirements and constraints

Ask about input size, tree balance, and whether recursion is acceptable. This shows you consider practical implications.

2. Explain recursive approach

Describe the simple recursive solution: traverse left, visit node, traverse right. Mention its O(n) time and O(h) space complexity.

3. Present iterative approach with stack

Detail the iterative method using an explicit stack to simulate recursion, highlighting its O(n) time and O(h) space complexity.

4. Discuss Morris traversal (optional)

If time permits, explain Morris traversal for O(1) space, noting it temporarily modifies the tree and restores it.

5. Analyze complexity and trade-offs

Compare time and space complexities of each approach, and discuss when to use which based on constraints.

Key Points to Mention

  • Definition of inorder traversal: left subtree, root, right subtree.
  • Recursive solution: simple but uses call stack, risk of stack overflow for deep trees.
  • Iterative solution: uses explicit stack, more control, avoids recursion limits.
  • Time complexity: O(n) for all approaches, as each node is visited once.
  • Space complexity: O(h) for recursive and iterative stack, O(1) for Morris traversal.
  • Morris traversal: modifies tree temporarily, no extra space, but complex to implement.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.