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Amazon·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Amazon SWE coding round, one question on tree traversal. Pretty short session, nothing wild.

Questions Asked (1)

Q1

Implement an inorder traversal for an N-ary tree.

Algorithms & Data Structures
Author's notes

Tricky part is that inorder for N-ary isn't as cleanly defined as it is for binary trees.

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AI HintsAI Generated

Suggested Approach

Clarify the definition of inorder traversal for an N-ary tree, as it is not standard. Then present both recursive and iterative solutions, explaining the time and space complexity. Discuss potential variations and edge cases.

Pro tip: Acknowledge that inorder traversal for N-ary trees is ambiguous and propose a reasonable definition (e.g., visit children before the root, or visit the first child, then root, then remaining children). This shows you understand tree traversals deeply and can handle underspecified problems.

1. Clarify the problem

Ask the interviewer to define inorder traversal for an N-ary tree, or state your assumption clearly. For example, you might define it as visiting the first child, then the root, then the remaining children.

2. Choose an approach

Decide between recursive and iterative solutions. Recursive is simpler; iterative may be preferred for large trees to avoid stack overflow.

3. Implement the solution

Write clean code for the chosen approach. For recursion, define a helper function that processes children in order. For iteration, use a stack to simulate the recursion.

4. Analyze complexity

State that both time and space complexity are O(N) for N nodes, with space O(H) for recursion stack or explicit stack, where H is the height of the tree.

5. Test with examples

Walk through a simple example, such as a tree with root and two children, to verify the traversal order. Discuss edge cases like empty tree or single node.

Key Points to Mention

  • Definition of inorder traversal for N-ary trees is not standard; clarify or state assumption.
  • Recursive solution: process first child, then root, then remaining children (or similar).
  • Iterative solution using a stack, handling the root visit between children.
  • Time complexity O(N) and space complexity O(H) for balanced trees, O(N) worst-case.
  • Edge cases: empty tree, single node, skewed tree.
  • Potential variations: preorder and postorder traversals for N-ary trees.

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