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

Senior
Apr 2026

Summary

OpenAI SWE interview with a multi-part combat simulation coding problem. Three incremental sub-questions building on each other, which is a format I hadn't prepped for specifically and it showed.

Questions Asked (1)

Q1

Implement a monster fighting / combat simulation across three incremental parts, where each part builds on the previous one.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

The three-part structure is what got me.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and assumptions for each part, then design a clean object-oriented model with extensible interfaces. Implement incrementally, ensuring each part is testable and builds on the previous without major refactoring. Discuss trade-offs between simplicity and flexibility, and consider performance implications as complexity grows.

Pro tip: Demonstrate foresight by designing interfaces that anticipate future extensions (e.g., new monster types, abilities) from the start, but avoid over-engineering. This shows you can balance immediate needs with long-term maintainability.

1. Clarify Requirements and Assumptions

Ask clarifying questions about each part: what entities exist, how combat is resolved, what metrics matter (e.g., turn-based, real-time, damage calculation). State assumptions explicitly to align with the interviewer.

2. Design Core Abstractions

Identify key classes/interfaces (e.g., Monster, Player, CombatEngine, Ability) and their relationships. Use design patterns like Strategy for abilities or Observer for events to keep the system extensible.

3. Implement Part 1: Basic Combat

Build a minimal working version: two entities with health and attack, simple turn-based loop. Focus on correctness and clean code, with unit tests for core logic.

4. Extend for Part 2 and Part 3

Incrementally add features (e.g., multiple monsters, special abilities, status effects) by extending abstractions. Refactor only when necessary, and discuss how changes affect design and performance.

5. Analyze Trade-offs and Test

Discuss trade-offs (e.g., inheritance vs. composition, performance vs. flexibility) and ensure the solution is testable. Mention edge cases and how you would validate each part.

Key Points to Mention

  • Object-oriented design principles: encapsulation, inheritance, polymorphism, and composition over inheritance.
  • Design patterns: Strategy for abilities, Factory for monster creation, Observer for event handling.
  • Extensibility: how to add new monster types or abilities without modifying existing code (Open/Closed Principle).
  • Testing: unit tests for combat logic, mocking for randomness, and integration tests for multi-part scenarios.
  • Performance considerations: time complexity of combat resolution, memory usage for large numbers of entities.
  • Trade-offs: simplicity vs. flexibility, over-engineering vs. future-proofing, and when to refactor.

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