The core insight is storing the inverse of each operation on a stack rather than snapshotting the whole buffer each time.
Start by clarifying requirements and constraints, then propose a design using two stacks (undo and redo) for O(1) operations, and discuss how to handle the text buffer efficiently. Explain the trade-offs between different approaches and consider edge cases like redo clearing and memory management.
Pro tip: Mention that you can optimize memory by storing deltas (e.g., inserted/deleted text and position) instead of full snapshots, and discuss how to handle large text buffers with a piece table or gap buffer for efficiency.
Ask about expected operation frequencies, text buffer size, memory limits, and whether undo/redo history needs to be persisted. Confirm that all operations should be O(1) or O(log n).
Propose using a text buffer (e.g., dynamic array, gap buffer, or piece table) for efficient insert/delete, and two stacks (undo and redo) to store operations. Each operation should record enough information to reverse it.
Specify how insert and delete modify the buffer and push onto the undo stack, how undo pops from undo and pushes onto redo, how redo pops from redo and pushes onto undo, and that any new operation clears the redo stack.
Discuss time and space complexity: O(1) for undo/redo stack operations, and O(1) or O(n) for buffer modifications depending on the data structure. Compare storing full snapshots vs. deltas, and mention memory overhead.
Address edge cases: undo/redo when stacks are empty, redo clearing on new operation, and potential memory growth. Suggest extensions like grouping operations or limiting history size.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.