"use strict";
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const DoublyLinkedList = require("./DoublyLinkedList");
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const DequeIterator = require("./DequeIterator");
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/**
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* DoublyLinkedList backed double ended queue
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* implements just enough to keep the Pool
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*/
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class Deque {
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constructor() {
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this._list = new DoublyLinkedList();
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}
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/**
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* removes and returns the first element from the queue
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* @return {any} [description]
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*/
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shift() {
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if (this.length === 0) {
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return undefined;
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}
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const node = this._list.head;
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this._list.remove(node);
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return node.data;
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}
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/**
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* adds one elemts to the beginning of the queue
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* @param {any} element [description]
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* @return {any} [description]
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*/
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unshift(element) {
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const node = DoublyLinkedList.createNode(element);
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this._list.insertBeginning(node);
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}
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/**
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* adds one to the end of the queue
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* @param {any} element [description]
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* @return {any} [description]
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*/
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push(element) {
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const node = DoublyLinkedList.createNode(element);
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this._list.insertEnd(node);
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}
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/**
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* removes and returns the last element from the queue
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*/
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pop() {
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if (this.length === 0) {
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return undefined;
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}
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const node = this._list.tail;
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this._list.remove(node);
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return node.data;
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}
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[Symbol.iterator]() {
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return new DequeIterator(this._list);
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}
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iterator() {
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return new DequeIterator(this._list);
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}
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reverseIterator() {
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return new DequeIterator(this._list, true);
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}
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/**
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* get a reference to the item at the head of the queue
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* @return {any} [description]
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*/
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get head() {
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if (this.length === 0) {
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return undefined;
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}
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const node = this._list.head;
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return node.data;
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}
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/**
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* get a reference to the item at the tail of the queue
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* @return {any} [description]
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*/
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get tail() {
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if (this.length === 0) {
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return undefined;
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}
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const node = this._list.tail;
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return node.data;
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}
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get length() {
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return this._list.length;
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}
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}
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module.exports = Deque;
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