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101 lines (95 loc) · 2.43 KB
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/**
* Keeps track of a set of elements partitioned into a
* number of disjoint (nonoverlapping) subsets.
* Allows to check whether the path between two nodes exists.
* <br>
* The algorithm is inspired by Robert Sedgewick's Java implementation.
* For further reading http://algs4.cs.princeton.edu/home/.
*
* @example
*
* var QuickUnion = require('path-to-algorithms/' +
* 'src/sets/weightquickunion').QuickUnion;
*
* var qunion = new QuickUnion(10);
* qunion.union(0, 1);
* qunion.union(2, 1);
* qunion.union(3, 4);
* qunion.union(8, 9);
* qunion.union(4, 8);
*
* console.log(qunion.connected(0, 9)); // false
* console.log(qunion.connected(3, 9)); // true
*
* @public
* @module sets/weightquickunion
*/
(function (exports) {
'use strict';
/**
* Initialization.<br><br>
* Time complexity: O(N).
*
* @public
* @constructor
* @param {Numner} size Count of the nodes.
*/
exports.QuickUnion = function (n) {
this._ids = [];
this._size = [];
for (var i = 0; i < n; i += 1) {
this._ids[i] = i;
this._size[i] = 1;
}
};
/**
* Finds the root of given node.<br><br>
* Time complexity: O(log N).
* @private
* @param {Number} i The given node.
* @return {Number} Root of the given node.
*/
exports.QuickUnion.prototype._root = function (i) {
while (i !== this._ids[i]) {
// this._ids[i] = this._ids[this._ids[i]]; //enables the path compression
i = this._ids[i];
}
return i;
};
/**
* Checks whether two nodes are connected.<br><br>
* Time complexity: O(log N).
*
* @param {Number} p The first node.
* @param {Number} q The second node.
* @return {Boolean} True/false depending on whether the nodes are connected.
*/
exports.QuickUnion.prototype.connected = function (p, q) {
return this._root(p) === this._root(q);
};
/**
* Connects two nodes - p and q.<br><br>
* Time complexity: O(log N).
*
* @public
* @method
* @param {Number} p The first node.
* @param {Number} q The second node.
*/
exports.QuickUnion.prototype.union = function (p, q) {
var pf = this._root(p);
var qf = this._root(q);
if (pf === qf) {
return; // already linked
}
var psz = this._size[qf];
var qsz = this._size[pf];
if (psz < qsz) {
this._ids[pf] = qf;
this._size[qf] += psz;
} else {
this._ids[qf] = pf;
this._size[pf] += qsz;
}
};
})(typeof window === 'undefined' ? module.exports : window);