Design
Text Editor with Undo/Redo
Design a simple text editor supporting insert, delete, and multi-level undo/redo of edits.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
It pairs the Command pattern with a real data-structure decision (how to represent large mutable text) — a good test of whether you think about scale even in a "simple" feature.
02 - Where this system exists in the real world
You interact with this design every day.
Text editors and IDEs (undo/redo stacks)
Word processors with edit history
Collaborative document editors
03 - What you'll master
Solve this once. Know it forever.
Apply Command pattern to insert/delete operations
Manage undo/redo stack branching correctly
Consider efficient text storage for large documents
04 - What you'll design
6 functional · 2 non-functional requirements.
Insert text at a given cursor position
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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