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102 lines
2.4 KiB
JavaScript
102 lines
2.4 KiB
JavaScript
/**
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* Keeps track of a set of elements partitioned into a
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* number of disjoint (nonoverlapping) subsets.
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* Allows to check whether the path between two nodes exists.
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* <br>
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* The algorithm is inspired by Robert Sedgewick's Java implementation.
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* {@link http://algs4.cs.princeton.edu/home/}
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*
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* @example
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*
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* var QuickUnion = require('path-to-algorithms/' +
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* 'src/sets/weightquickunion').QuickUnion;
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*
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* var qunion = new QuickUnion(10);
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* qunion.union(0, 1);
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* qunion.union(2, 1);
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* qunion.union(3, 4);
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* qunion.union(8, 9);
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* qunion.union(4, 8);
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*
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* console.log(qunion.connected(0, 9)); // false
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* console.log(qunion.connected(3, 9)); // true
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*
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* @public
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* @module sets/weightquickunion
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*/
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(function (exports) {
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'use strict';
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/**
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* Initialization.<br><br>
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* Time complexity: O(N).
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*
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* @public
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* @constructor
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* @param {Numner} size Count of the nodes.
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*/
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exports.QuickUnion = function (n) {
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this._ids = [];
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this._size = [];
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for (var i = 0; i < n; i += 1) {
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this._ids[i] = i;
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this._size[i] = 1;
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}
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};
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/**
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* Finds the root of given node.<br><br>
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* Time complexity: O(log N).
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* @private
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* @param {Number} i The given node.
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* @return {Number} Root of the given node.
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*/
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exports.QuickUnion.prototype._root = function (i) {
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while (i !== this._ids[i]) {
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// this._ids[i] = this._ids[this._ids[i]]; //enables the path compression
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i = this._ids[i];
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}
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return i;
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};
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/**
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* Checks whether two nodes are connected.<br><br>
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* Time complexity: O(log N).
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*
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* @param {Number} p The first node.
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* @param {Number} q The second node.
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* @return {Boolean} True/false depending on whether the nodes are connected.
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*/
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exports.QuickUnion.prototype.connected = function (p, q) {
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return this._root(p) === this._root(q);
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};
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/**
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* Connects two nodes - p and q.<br><br>
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* Time complexity: O(log N).
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*
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* @public
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* @method
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* @param {Number} p The first node.
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* @param {Number} q The second node.
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*/
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exports.QuickUnion.prototype.union = function (p, q) {
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var pf = this._root(p);
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var qf = this._root(q);
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if (pf === qf) {
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return; // already linked
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}
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var psz = this._size[qf];
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var qsz = this._size[pf];
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if (psz < qsz) {
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this._ids[pf] = qf;
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this._size[qf] += psz;
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} else {
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this._ids[qf] = pf;
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this._size[pf] += qsz;
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}
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};
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})(typeof window === 'undefined' ? module.exports : window);
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