algorithmpool/src/dspool/set/disjoint_set.js

A pool of algorithms and data-structures for geeks

import {DisjointSetItem} from './DisjointSetItem';

export class DisjointSet {

    constructor(keyCallback) {
        this.keyCallback = keyCallback;
        this.items = {};
    }

    makeSet(itemValue) {
        const disjointSetItem = new DisjointSetItem(itemValue, this.keyCallback);

        if (!this.items[disjointSetItem.getKey()]) {
            // Add new item only in case if it not presented yet.
            this.items[disjointSetItem.getKey()] = disjointSetItem;
        }

        return this;
    }

    find(itemValue) {
        const templateDisjointItem = new DisjointSetItem(itemValue, this.keyCallback);

        // Try to find item itself;
        const requiredDisjointItem = this.items[templateDisjointItem.getKey()];

        if (!requiredDisjointItem) {
            return null;
        }

        return requiredDisjointItem.getRoot().getKey();
    }

    union(valueA, valueB) {
        const rootKeyA = this.find(valueA);
        const rootKeyB = this.find(valueB);

        if (rootKeyA === null || rootKeyB === null) {
            throw new Error('One or two values are not in sets');
        }

        if (rootKeyA === rootKeyB) {
            // In case if both elements are already in the same set then just return its key.
            return this;
        }

        const rootA = this.items[rootKeyA];
        const rootB = this.items[rootKeyB];

        if (rootA.getRank() < rootB.getRank()) {
            // If rootB's tree is bigger then make rootB to be a new root.
            rootB.addChild(rootA);

            return this;
        }

        // If rootA's tree is bigger then make rootA to be a new root.
        rootA.addChild(rootB);

        return this;
    }

    inSameSet(valueA, valueB) {
        const rootKeyA = this.find(valueA);
        const rootKeyB = this.find(valueB);

        if (rootKeyA === null || rootKeyB === null) {
            throw new Error('One or two values are not in sets');
        }

        return rootKeyA === rootKeyB;
    }
}