jiapengyu
101 lines
2.3 KiB
JavaScript
101 lines
2.3 KiB
JavaScript
/* -*- Mode: js; js-indent-level: 2; -*- */
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/*
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* Copyright 2011 Mozilla Foundation and contributors
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* Licensed under the New BSD license. See LICENSE or:
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* http://opensource.org/licenses/BSD-3-Clause
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*/
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/**
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* A data structure which is a combination of an array and a set. Adding a new
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* member is O(1), testing for membership is O(1), and finding the index of an
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* element is O(1). Removing elements from the set is not supported. Only
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* strings are supported for membership.
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*/
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class ArraySet {
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constructor() {
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this._array = []
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this._set = new Map()
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}
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/**
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* Static method for creating ArraySet instances from an existing array.
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*/
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static fromArray(aArray, aAllowDuplicates) {
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const set = new ArraySet()
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for (let i = 0, len = aArray.length; i < len; i++) {
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set.add(aArray[i], aAllowDuplicates)
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}
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return set
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}
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/**
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* Return how many unique items are in this ArraySet. If duplicates have been
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* added, than those do not count towards the size.
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*
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* @returns Number
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*/
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size() {
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return this._set.size
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}
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/**
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* Add the given string to this set.
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*
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* @param String aStr
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*/
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add(aStr, aAllowDuplicates) {
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const isDuplicate = this.has(aStr)
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const idx = this._array.length
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if (!isDuplicate || aAllowDuplicates) {
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this._array.push(aStr)
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}
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if (!isDuplicate) {
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this._set.set(aStr, idx)
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}
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}
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/**
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* Is the given string a member of this set?
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*
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* @param String aStr
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*/
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has(aStr) {
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return this._set.has(aStr)
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}
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/**
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* What is the index of the given string in the array?
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*
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* @param String aStr
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*/
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indexOf(aStr) {
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const idx = this._set.get(aStr)
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if (idx >= 0) {
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return idx
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}
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throw new Error('"' + aStr + '" is not in the set.')
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}
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/**
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* What is the element at the given index?
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*
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* @param Number aIdx
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*/
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at(aIdx) {
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if (aIdx >= 0 && aIdx < this._array.length) {
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return this._array[aIdx]
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}
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throw new Error('No element indexed by ' + aIdx)
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}
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/**
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* Returns the array representation of this set (which has the proper indices
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* indicated by indexOf). Note that this is a copy of the internal array used
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* for storing the members so that no one can mess with internal state.
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*/
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toArray() {
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return this._array.slice()
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}
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}
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exports.ArraySet = ArraySet
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