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Openai·Software Engineer·Technical Phone Screen·Senior

SeniorRejected
Apr 2026

Summary

Did a coding round for a Research Scientist role at OpenAI and walked away pretty sure I knew exactly where things went wrong. The problem was interesting but I think my solution approach didn't land the way I expected.

Questions Asked (1)

Q1

You have a set of Annotators, Models, and Questions. First, generate a list of (annotator, model, question) tuples such that each (model, question) pair appears as evenly as possible. Then extend this so that each annotator also sees a balanced distribution across different models.

Algorithms & Data StructuresSystem DesignTechnical Trade-offs
Author's notes

Went greedy pretty fast, felt good about it in the moment.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem constraints and defining what 'balanced' means (e.g., each (model, question) pair appears roughly equally often, and each annotator sees a similar distribution of models). Then propose a two-phase algorithm: first generate a balanced list of (model, question) pairs, then assign annotators to these pairs in a round-robin or greedy manner to balance model exposure per annotator. Discuss trade-offs like randomness vs determinism and scalability.

Pro tip: Mention that perfect balance may be impossible due to indivisibility, so aim for near-balance and consider using a randomized algorithm with a seed for reproducibility. Also, highlight the importance of monitoring and adjusting in production.

1. Clarify requirements and constraints

Ask questions to understand the scale (number of annotators, models, questions), whether each annotator must see each question at most once, and if there are any constraints on model exposure per annotator. Define 'balanced' precisely.

2. Design for balanced (model, question) pairs

Create a list where each (model, question) pair appears as evenly as possible. If total pairs T = M * Q, and we need N tuples, distribute the N occurrences across T pairs such that counts differ by at most 1. Use a round-robin or cyclic distribution.

3. Extend to balance annotator-model exposure

Assign annotators to the generated (model, question) pairs such that each annotator sees a balanced distribution of models. Use a greedy approach: for each annotator, assign pairs with models they've seen least, ensuring overall balance.

4. Analyze trade-offs and scalability

Discuss time/space complexity, potential need for randomization to avoid bias, and how the algorithm scales with large numbers. Mention alternative approaches like integer linear programming for optimal balance.

5. Test and validate

Propose test cases (e.g., small numbers, uneven counts) to verify balance. Suggest metrics to measure balance (e.g., max-min difference in counts) and how to handle edge cases.

Key Points to Mention

  • Definition of balance: each (model, question) pair appears as evenly as possible, and each annotator sees a balanced distribution of models.
  • Algorithm for generating balanced (model, question) pairs: use round-robin or cyclic distribution to achieve near-equal counts.
  • Assignment strategy for annotators: greedy or round-robin to balance model exposure per annotator.
  • Handling indivisibility: when counts cannot be perfectly equal, ensure the difference is at most 1.
  • Trade-offs: determinism vs randomness, optimality vs simplicity, and scalability considerations.
  • Validation: metrics to measure balance and test cases to ensure correctness.

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