merge-find

Implementation of Disjoint-set data structure algorithm (also called a union–find data structure or merge–find set) with TypeScript support.

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📝 Disjoint-set data structure algorithm

In computer science, a disjoint-set data structure, also called a union–find data structure or merge–find set, is a data structure that stores a collection of disjoint (non-overlapping) sets. Equivalently, it stores a partition of a set into disjoint subsets. It provides operations for adding new sets, merging sets (replacing them by their union), and finding a representative member of a set. The last operation makes it possible to find out efficiently if any two elements are in the same or different sets.

🚀 Installation

$3

``
npm install merge-find
`

$3

`
yarn add merge-find
`

👩‍💻 Usage

`ts
import {DisjointSet} from 'merge-find'

type MyNodeType = {
name: string
}

// instantiate disjoint-set data structure
const disjointSet = new DisjointSet()

// add nodes to the set
const id1 = disjointSet.add({
name: 'First node'
}) // 0

const id2 = disjointSet.add({
name: 'Second node'
}) // 1

const id3 = disjointSet.add({
name: 'Third node'
}) // 2

// Merge some nodes together
disjointSet.union(0, 1)

// Check if nodes are connected
disjointSet.areConnected(0, 1); // true
disjointSet.areConnected(0, 2); // false

// Number of subsets
disjointSet.numberOfSubsets(); // 2

// List of all subsets
disjointSet.subsets();
/* [ [ { id: 0, parent: -1, rank: 1, name: 'First node' },
{ id: 1, parent: 0, rank: 0, name: 'Second node' } ],
[ { id: 2, parent: -1, rank: 0, name: 'Third node' } ] ] */

// Subset containing a specific node
disjointSet.subset(2) // [ { id: 2, parent: -1, rank: 0, name: 'Third node' } ]
`

You can try it live on replit.

🌐 API

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|Factory|Description|
|---|---|
|new DisjointSet()|Instantiates disjoint-set data structure.|

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|Method|Return|Description|
|---|---|---|
|add(node: T)|Number|Creates a new subset consisting of the new element node.|
|union(id1: number, id2: number)|Void|Merges the two specified subsets (the subset in which the element a is located, and the subset in which the element b is located). The merge is by rank.|
|find(id: number)|DisjointSetNodeType|Returns the representative (the root node) of the subset that contains the element with and id id.|
|areConnected(id1: number, id2: number)|Boolean|Check if 2 nodes are connected (in the same subset).|
|numberOfSubsets()|Number|It returns the number of subsets in the set.|
|subsets()|DisjointSetNodeType[][]|It returns a list of all subsets. Each subset is an array of elements contained in that subset.|
|subset(id: number)|DisjointSetNodeType[]|It returns an array of elements in the subset containing element with and id id.|
|destroy()|void|It resets the set list to an empty array.|

$3

The DisjointSetNodeType type is:

`ts
type DisjointSetNodeType = T & {
id: number
parent: number
rank: number
}
``

📌 References

- Disjoint-set data structure (Wikipedia)
- Disjoint Set Union (Algorithms for Competitive Programming)