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Meta·Software Engineer·Onsite - Coding / Algorithms·Senior

Senior
May 2026

Summary

Meta SWE onsite coding round with an AI-focused problem. The question was geography-oriented and required implementing an algorithm from scratch, plus writing unit tests to verify correctness.

Questions Asked (1)

Q1

Implement a geography-related AI algorithm that works with map or location data, including debugging and unit test coverage.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

This wasn't a leetcode-style question you can just pattern-match your way through.

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AI HintsAI Generated

Suggested Approach

Clarify the geography problem (e.g., nearest point of interest, route optimization) and choose an appropriate algorithm like k-d tree or Dijkstra. Then implement it with clean code, write unit tests covering edge cases, and debug systematically using logging and assertions.

Pro tip: Before coding, discuss trade-offs between different spatial data structures (e.g., k-d tree vs. quadtree) and their impact on performance and memory, showing you consider real-world constraints. Also, mention how you would handle floating-point precision issues in geographic calculations.

1. Clarify requirements and constraints

Ask questions to understand the exact problem, data size, expected query patterns, and performance requirements. Confirm whether it's a one-time computation or needs to support dynamic updates.

2. Choose algorithm and data structures

Select an appropriate spatial algorithm (e.g., k-d tree for nearest neighbor, Dijkstra for shortest path) and justify your choice based on trade-offs like time complexity, memory, and ease of implementation.

3. Implement with modular, testable code

Write clean, modular functions for core logic (e.g., distance calculation, tree building) and separate I/O. Use meaningful variable names and add comments for complex parts.

4. Write comprehensive unit tests

Cover normal cases, edge cases (empty input, single point, points on boundaries), and error conditions. Use mocking for external dependencies and test for floating-point precision.

5. Debug systematically and discuss improvements

Use print statements, debuggers, or logging to trace issues. After fixing, discuss potential optimizations (e.g., caching, indexing) and how you would scale the solution.

Key Points to Mention

  • Spatial data structures: k-d tree, quadtree, R-tree, and their trade-offs
  • Distance metrics: Haversine formula for great-circle distance, Euclidean for projected coordinates
  • Algorithm complexity: time and space complexity of chosen approach and its impact on large datasets
  • Unit testing: edge cases, floating-point precision, and mocking external services
  • Debugging techniques: logging, assertions, and using debuggers to isolate issues
  • Trade-offs: accuracy vs. performance, memory vs. speed, and simplicity vs. scalability

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