DisjointSetItem.js

export default class DisjointSetItem {
 /**
 * @param {*} value
 * @param {function(value: *)} [keyCallback]
 */
 constructor(value, keyCallback) {
 this.value = value;
 this.keyCallback = keyCallback;
 /** @var {DisjointSetItem} this.parent */
 this.parent = null;
 this.children = {};
 }

 /**
 * @return {*}
 */
 getKey() {
 // Allow user to define custom key generator.
 if (this.keyCallback) {
 return this.keyCallback(this.value);
 }

 // Otherwise use value as a key by default.
 return this.value;
 }

 /**
 * @return {DisjointSetItem}
 */
 getRoot() {
 return this.isRoot() ? this : this.parent.getRoot();
 }

 /**
 * @return {boolean}
 */
 isRoot() {
 return this.parent === null;
 }

 /**
 * Rank basically means the number of all ancestors.
 *
 * @return {number}
 */
 getRank() {
 if (this.getChildren().length === 0) {
 return 0;
 }

 let rank = 0;

 /** @var {DisjointSetItem} child */
 this.getChildren().forEach((child) => {
 // Count child itself.
 rank += 1;

 // Also add all children of current child.
 rank += child.getRank();
 });

 return rank;
 }

 /**
 * @return {DisjointSetItem[]}
 */
 getChildren() {
 return Object.values(this.children);
 }

 /**
 * @param {DisjointSetItem} parentItem
 * @param {boolean} forceSettingParentChild
 * @return {DisjointSetItem}
 */
 setParent(parentItem, forceSettingParentChild = true) {
 this.parent = parentItem;
 if (forceSettingParentChild) {
 parentItem.addChild(this);
 }

 return this;
 }

 /**
 * @param {DisjointSetItem} childItem
 * @return {DisjointSetItem}
 */
 addChild(childItem) {
 this.children[childItem.getKey()] = childItem;
 childItem.setParent(this, false);

 return this;
 }
}