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Meta·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Meta SWE interview with a tree problem. Pretty standard stuff but worth sharing for anyone prepping.

Questions Asked (1)

Q1

Given the roots of two binary trees, write a function to determine whether the two trees are identical, meaning they have the same structure and the same node values at every position.

Algorithms & Data Structures
Author's notes

Classic recursion problem.

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AI HintsAI Generated

Suggested Approach

Use a recursive depth-first traversal to compare the two trees simultaneously. At each step, check if both nodes are null (return true), if one is null (return false), or if their values differ (return false). Then recursively check the left and right subtrees.

Pro tip: Mention that this problem is a classic example of structural recursion and that the same pattern extends to checking subtree equality or symmetry. Also, note that an iterative BFS approach using a queue is possible, but recursion is cleaner and more intuitive.

1. Clarify the problem

Confirm that 'identical' means same structure and same node values at every position. Ask if the trees can be empty or have duplicate values.

2. Define the base cases

If both nodes are null, they are identical. If one is null and the other is not, they are not identical.

3. Compare current nodes

Check if the values of the current nodes are equal. If not, return false.

4. Recurse on subtrees

Recursively check if the left subtrees are identical and if the right subtrees are identical. Return true only if both are true.

5. Analyze complexity

State that time complexity is O(n) where n is the number of nodes, and space complexity is O(h) for recursion stack, where h is the height of the tree.

Key Points to Mention

  • Base cases: both null, one null
  • Value comparison at each node
  • Recursive calls on left and right children
  • Time complexity O(n) and space complexity O(h)
  • Edge cases: empty trees, single node trees, trees with different structures but same values
  • Alternative iterative approach using a queue (BFS)

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