Implement a Set with Readable Snapshots
Company: OpenAI
Role: Software Engineer
Category: Software Engineering Fundamentals
Difficulty: hard
Interview Round: Onsite
Overview: Implement a set that supports `add(value)`, `remove(value)`, `contains(value)`, `snapshot()`, and `containsAt(snapshot_id, value)`. Make the API or object boundaries explicit, then cover invariants, edge cases, testing strategy, and operational trade-offs.
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