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$ curl repovive.com/roadmaps/data-structures/persistent-data-structures/persistent-rope

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$ curl repovive.com/roadmaps/data-structures/persistent-data-structures/persistent-rope

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Persistent Rope - Persistent Data Structures | Data Structures | Repovive

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Data Structures19 sections · 729 units49h total

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Persistent Rope

Efficient string operations

A rope is a balanced binary tree for strings:

Leaves store string chunks
Internal nodes store length of left subtree

Ropes support efficient:

Concatenation: $O(\log n)$ by creating new root
Split: $O(\log n)$ by path copying
Index access: $O(\log n)$ using lengths

Persistent ropes enable undo/redo in text editors:

versions := []
function edit(version, pos, text)
    newRope := insert(versions[version], pos, text)
    versions.append(newRope)

function undo()
    return versions[len(versions) - 2]

Each edit creates a new version sharing most of the old rope.