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95 lines
2.3 KiB
95 lines
2.3 KiB
4 weeks ago
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/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Tobias Koppers @sokra
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*/
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"use strict";
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/**
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* intersect creates Set containing the intersection of elements between all sets
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* @template T
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* @param {Set<T>[]} sets an array of sets being checked for shared elements
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* @returns {Set<T>} returns a new Set containing the intersecting items
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*/
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const intersect = sets => {
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if (sets.length === 0) return new Set();
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if (sets.length === 1) return new Set(sets[0]);
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let minSize = Infinity;
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let minIndex = -1;
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for (let i = 0; i < sets.length; i++) {
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const size = sets[i].size;
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if (size < minSize) {
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minIndex = i;
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minSize = size;
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}
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}
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const current = new Set(sets[minIndex]);
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for (let i = 0; i < sets.length; i++) {
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if (i === minIndex) continue;
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const set = sets[i];
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for (const item of current) {
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if (!set.has(item)) {
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current.delete(item);
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}
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}
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}
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return current;
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};
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/**
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* Checks if a set is the subset of another set
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* @template T
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* @param {Set<T>} bigSet a Set which contains the original elements to compare against
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* @param {Set<T>} smallSet the set whose elements might be contained inside of bigSet
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* @returns {boolean} returns true if smallSet contains all elements inside of the bigSet
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*/
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const isSubset = (bigSet, smallSet) => {
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if (bigSet.size < smallSet.size) return false;
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for (const item of smallSet) {
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if (!bigSet.has(item)) return false;
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}
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return true;
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};
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/**
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* @template T
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* @param {Set<T>} set a set
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* @param {function(T): boolean} fn selector function
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* @returns {T | undefined} found item
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*/
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const find = (set, fn) => {
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for (const item of set) {
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if (fn(item)) return item;
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}
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};
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/**
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* @template T
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* @param {Set<T>} set a set
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* @returns {T | undefined} first item
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*/
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const first = set => {
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const entry = set.values().next();
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return entry.done ? undefined : entry.value;
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};
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/**
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* @template T
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* @param {Set<T>} a first
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* @param {Set<T>} b second
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* @returns {Set<T>} combined set, may be identical to a or b
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*/
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const combine = (a, b) => {
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if (b.size === 0) return a;
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if (a.size === 0) return b;
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const set = new Set(a);
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for (const item of b) set.add(item);
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return set;
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};
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module.exports.intersect = intersect;
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module.exports.isSubset = isSubset;
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module.exports.find = find;
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module.exports.first = first;
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module.exports.combine = combine;
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