Implement an Undo/Redo System with Command Pattern
Last updated: April 5, 2025
Quick Overview
Design and implement an undo/redo system using the command pattern that supports arbitrary operations, grouping of operations, and memory-efficient history management.
Canva
April 5, 202512
7
2,567 solved
Design and implement an undo/redo system using the command pattern that supports arbitrary operations, grouping of operations, and memory-efficient history management.
Undo/redo is a core feature in any design editor. At Canva, the undo system must handle complex operations (move, resize, change color, group elements, apply effects) and support both single-user and collaborative contexts. This question tests your design pattern knowledge and practical engineering skills.
What the Interviewer Expects
- Implement the Command interface with execute and undo methods
- Build an UndoManager that maintains history stacks for undo and redo
- Support grouping multiple commands into a single undoable operation
- Implement memory management (limit history size, compress old commands)
- Write clean, extensible code that new command types can easily plug into
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you extend this to support undo in a collaborative editing context?
- How would you implement selective undo (undo a specific operation from the middle of the history)?
- How would you serialize the command history for persistence?
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Problem Analysis
The problem requires implementing an undo/redo system using the command pattern. The command pattern is suitable here because it encapsulates all the information needed to perform an action, allowing ...
Approach
- Define the Command Interface: Create a
Commandinterface withexecute()andundo()methods. 2. Implement Concrete Commands: For each operation (e.g.,MoveCommand, `ResizeCommand...
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