union-find

union-find

A basic union-find data structure for node.js. For more information, see wikipdia:

Disjoint Set Datastructures

Union find data structures solve the incremental connectivity problem. (That is maintaining a spanning forest under incremental insertions of edges.) To handle fully dynamic connectivity, you can use a dynamic forest data structure.

Usage

Here is an example showing how to do connected component labelling. Assume we are given a graph with VERTEX_COUNT vertices and a list of edges stored in array represented by pairs of vertex indices:

//Import data structure
var UnionFind = require('union-find')

var VERTEX_COUNT = 8
var edges = [
    [0,1],
    [1,2],
    [2,3],
    [5,6],
    [7,1]
]

//Link all the nodes together
var forest = new UnionFind(VERTEX_COUNT)
for(var i=0; i<edges.length; ++i) {
  forest.link(edges[i][0], edges[i][1])
}

//Label components
var labels = new Array(VERTEX_COUNT)
for(var i=0; i<VERTEX_COUNT; ++i) {
  labels[i] = forest.find(i)
}

Installation

npm install union-find

API

var UnionFind = require('union-find')

Constructor

var forest = new UnionFind(numVertices)

Creates a new union-find data structure.

• numVertices is the number of vertices in the graph

Returns A new union-find data structure

Methods

forest.length

Returns the number of vertices in the forest

forest.makeSet()

Creates a new vertex

Returns An integer id for the new vertex

forest.find(v)

Returns an identifier representing the connected component of any given vertex

Returns An integer id representing the connected component of v

forest.link(s, t)

Links a pair of connected components together

• s and t are both vertices

Credits

(c) 2013-2014 Mikola Lysenko. MIT License