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$ curl repovive.com/roadmaps/data-structures/persistent-data-structures/application-undo-redo

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$ curl repovive.com/roadmaps/data-structures/persistent-data-structures/application-undo-redo

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Application: Undo/Redo - Persistent Data Structures | Data Structures | Repovive

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Data Structures19 sections · 729 units49h total

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Application: Undo/Redo

Editor history

Text editors use persistent structures for undo/redo:

class Editor:
 versions: list of document states
 current: int // current version index

 function edit(operation)
 // Discard future versions (can't redo after new edit)
 versions := versions[0..current + 1]
 newDoc := apply(operation, versions[current])
 versions.append(newDoc)
 current := current + 1

 function undo()
 if current > 0 then
 current := current - 1

 function redo()
 if current < len(versions) - 1 then
 current := current + 1

With persistent structures, "discard future versions" is optional. You can keep all branches.