The undo/redo skeleton felt familiar but I fumbled the redo invalidation rule.
Start by clarifying requirements and constraints, then propose a layered architecture with a command pattern for undo/redo. Discuss data structures for layers and the undo/redo stacks, and explicitly address edge cases and trade-offs.
Pro tip: Demonstrate awareness of real-world constraints like memory usage and performance by suggesting optimizations such as command compression or snapshotting, and tie your design to Figma's collaborative editing context.
Ask questions to understand expected scale, layer types, operations, and whether undo/redo should be global or per-layer. Confirm if real-time collaboration is needed.
Propose a layered model (e.g., list of layers with z-index) and a command pattern for operations. Use two stacks for undo and redo, and consider using a doubly-linked list or array for layers.
Define how each operation (add, remove, reorder, edit) is encapsulated as a command with execute and undo methods. Explain how undo/redo stacks are updated and how new operations clear the redo stack.
Address undoing when the stack is empty (no-op or disable UI), redoing when empty, and clearing redo history on new operations. Discuss handling of failed operations and memory management.
Compare command pattern vs. snapshotting for memory and performance. Suggest optimizations like command merging, lazy snapshots, or persistent data structures for scalability.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.