Meta·Software Engineer·Technical Phone Screen·Senior

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Apr 2026Remote

Summary

Meta infrastructure engineer round, basically one coding problem the whole time. The problem itself wasn't hard conceptually but I fumbled the implementation more than I'd like to admit, and the follow-up discussion about memory tradeoffs was where things got interesting.

Questions Asked (1)

Given an immutable linked list where you can only call printValue() and getNext(), print all node values in reverse order. Then walk through multiple approaches with different time/space tradeoffs.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I knew recursion immediately and coded it up fine.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the constraints: the list is immutable, and only printValue() and getNext() are available. Then present a recursive solution that uses the call stack to reverse the order, followed by iterative approaches using an explicit stack or a doubly linked list if mutation were allowed, discussing time/space tradeoffs.

Pro tip: Emphasize that recursion depth is a concern for large lists and propose an iterative solution with an explicit stack to avoid stack overflow, showing awareness of production constraints.

1. Clarify constraints and requirements

Confirm that the list is immutable, only printValue() and getNext() are available, and that we need to print values in reverse order without modifying the list.

2. Recursive approach

Traverse to the end recursively, then print on the way back. This uses O(n) stack space and O(n) time.

3. Iterative with explicit stack

Traverse the list iteratively, pushing values onto a stack, then pop and print. This also uses O(n) space but avoids recursion depth limits.

4. Alternative: reverse list if mutable

If the list were mutable, reverse it in place, print, and reverse back. This uses O(1) extra space but modifies the list, which is not allowed here.

5. Compare tradeoffs

Discuss time/space complexity: all approaches are O(n) time; recursion and stack are O(n) space; in-place reversal is O(1) space but requires mutability. Mention that recursion may cause stack overflow for large n.

Key Points to Mention

Time complexity: O(n) for all approaches.
Space complexity: O(n) for recursion and explicit stack; O(1) for in-place reversal if allowed.
Immutability constraint prevents in-place reversal.
Recursion depth may cause stack overflow for large lists.
Explicit stack avoids recursion depth limits but still uses O(n) space.
If the list were doubly linked, we could traverse backwards without extra space.

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