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Airbnb·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Jun 2026

Summary

Airbnb software engineer interview with a grid-based scoring problem that looks deceptively simple until you actually try to write test cases for it yourself.

Questions Asked (1)

Q1

You're given a 5x5 board where each cell encodes a terrain type and a crown count (e.g. 'G1' for grass with 1 crown). Find every maximal 4-directionally-connected region of cells with the same terrain type, then for each region multiply the total crowns in it by the region's size. Return the sum across all regions. Also write your own test cases.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

The algorithm itself is basically flood fill, BFS or DFS, not too bad.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem and edge cases, then propose a solution using graph traversal (BFS/DFS) to find connected components, compute the score for each, and sum them. Discuss time/space complexity and trade-offs, and outline test cases including edge cases.

Pro tip: Demonstrate maturity by discussing how to handle large boards with memory constraints, and mention that you would write unit tests for edge cases like empty board or single cell.

1. Clarify the problem

Ask questions to confirm understanding: input format, terrain types, crown counts, connectivity definition, and expected output. Confirm edge cases like empty board or no crowns.

2. Outline the algorithm

Propose using BFS/DFS to find connected components of same terrain. For each component, track size and sum of crowns, then compute product and add to total.

3. Analyze complexity and trade-offs

State time complexity O(N*M) and space O(N*M) for visited tracking. Discuss iterative vs recursive DFS to avoid stack overflow, and possible optimizations.

4. Design test cases

List test cases: all same terrain, all different, mixed, single cell, empty board, board with zero crowns, and large board for performance.

5. Summarize and conclude

Reiterate the approach, mention potential pitfalls (e.g., integer overflow), and express confidence in implementation.

Key Points to Mention

  • Use BFS/DFS for connected components
  • Track visited cells to avoid revisiting
  • Compute region size and total crowns during traversal
  • Time complexity O(N*M) and space O(N*M)
  • Consider iterative DFS to prevent stack overflow
  • Write comprehensive test cases including edge cases

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