Text Editor in Four Stages: Buffer, Undo/Redo, Trie Autocomplete, Collaborative OT

Text Editor in Four Stages: Buffer, Undo/Redo, Trie Autocomplete, Collaborative OT

Company: OpenAI

Role: Software Engineer

Category: Software Engineering Fundamentals

Difficulty: hard

Interview Round: Onsite

Overview: Build a text editor in four stages: a buffer with insert, delete and read, undo and redo with two stacks, trie-based autocomplete ranked by word frequency, and real-time collaborative editing with operational transformation. It tests data structure choice, reversible operations, top-k retrieval and concurrency correctness.