Design a text editor with undo
Medium35 minFree, no account
Two stacks and a data structure choice that decides whether it is usable on a large file.
The question
Design the core of a text editor: insert, delete, cursor movement, undo and redo.
It must stay responsive on a 10MB file, and typing twenty characters should undo as one action, not twenty.
Functional
- Insert and delete at the cursor; select a range and replace it.
- Unlimited undo and redo.
- Consecutive typing coalesces into one undoable action.
- Find and replace.
Non-functional
- Edits in the middle of a 10MB file must not be O(n).
- Undo history must not grow without bound in memory.
35:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.
Stuck?
0 of 3 hints takenThe worked solution
written by a person · not a gradeScore yourself
0 of 5 marked- Chose a buffer structure with a stated reason and threshold25
- Commands that carry their own inverse, including captured deleted text25
- Two stacks with redo cleared on a new edit20
- Coalescing rules, including what breaks a run20
- Bounded history by memory, not entry count10
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