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LinkedIn·Mobile Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

LinkedIn mobile engineer interview with a weighted nested list problem. Pretty standard algorithmic round but the inverse-depth weighting twist made me second-guess myself more than I'd like to admit.

Questions Asked (1)

Q1

Given a nested list of integers where each element can be an integer or another nested list, compute a weighted sum where each integer's weight is (maxDepth - depth + 1). Deeper integers get lower weight.

Algorithms & Data Structures
Author's notes

I initially coded the straightforward version where deeper elements get more weight, which is the classic problem.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem and edge cases, then explain that you need to find the maximum depth before computing the weighted sum. Use a recursive DFS to compute max depth, then a second DFS to accumulate the weighted sum, or combine both in one pass by collecting values and depths.

Pro tip: Mention that you can avoid two passes by storing (value, depth) pairs during a single traversal, then compute maxDepth and sum afterward—this shows optimization awareness. Also, discuss handling large inputs iteratively to avoid stack overflow, which is crucial for mobile environments.

1. Clarify and Define

Restate the problem to ensure understanding, ask about constraints (e.g., list size, depth limits, integer range), and confirm the weight formula.

2. Choose Traversal Strategy

Decide between recursive DFS (simpler) or iterative BFS/DFS with a stack (safer for deep nesting). Explain the trade-offs.

3. Compute Max Depth

Traverse the nested list to find the maximum depth. This can be done in the same pass as collecting values or separately.

4. Calculate Weighted Sum

Traverse again (or use stored data) to compute the sum, applying weight = maxDepth - depth + 1 for each integer.

5. Analyze Complexity and Optimize

State time and space complexity (O(n) time, O(d) space for recursion). Discuss possible optimizations like single-pass or iterative approach.

Key Points to Mention

  • Recursive DFS to compute max depth and weighted sum
  • Iterative approach using stack to avoid recursion limit
  • Time complexity O(n) and space complexity O(d) where d is max depth
  • Handling edge cases: empty list, single integer, deeply nested lists
  • Single-pass optimization by storing values and depths
  • Mobile considerations: memory constraints, stack overflow risks

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