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Doubly Linked List Class - JavaScript
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| const Node = require('./Node'); | |
| class DoublyLinkedList { | |
| constructor() { | |
| this.head = null; | |
| this.tail = null; | |
| } | |
| addToHead(data) { | |
| const newHead = new Node(data); | |
| const currentHead = this.head; | |
| if (currentHead) { | |
| currentHead.setPreviousNode(newHead); | |
| newHead.setNextNode(currentHead); | |
| } | |
| this.head = newHead; | |
| if (!this.tail) { | |
| this.tail = newHead; | |
| } | |
| } | |
| addToTail(data) { | |
| const newTail = new Node(data); | |
| const currentTail = this.tail; | |
| if (currentTail) { | |
| currentTail.setNextNode(newTail); | |
| newTail.setPreviousNode(currentTail); | |
| } | |
| this.tail = newTail; | |
| if (!this.head) { | |
| this.head = newTail; | |
| } | |
| } | |
| removeHead() { | |
| const removedHead = this.head; | |
| if (!removedHead) { | |
| return; | |
| } | |
| this.head = removedHead.getNextNode(); | |
| if (this.head) { | |
| this.head.setPreviousNode(null); | |
| } | |
| if (removedHead === this.tail) { | |
| this.removeTail(); | |
| } | |
| return removedHead.data; | |
| } | |
| removeTail() { | |
| const removedTail = this.tail; | |
| if (!removedTail) { | |
| return; | |
| } | |
| this.tail = removedTail.getPreviousNode(); | |
| if (this.tail) { | |
| this.tail.setNextNode(null); | |
| } | |
| if (removedTail === this.head) { | |
| this.removeHead(); | |
| } | |
| return removedTail.data; | |
| } | |
| removeByData(data) { | |
| let nodeToRemove; | |
| let currentNode = this.head; | |
| while (currentNode !== null) { | |
| if (currentNode.data === data) { | |
| nodeToRemove = currentNode; | |
| break; | |
| } | |
| currentNode = currentNode.getNextNode(); | |
| } | |
| if (!nodeToRemove) { | |
| return null; | |
| } | |
| if (nodeToRemove === this.head) { | |
| this.removeHead(); | |
| } else if (nodeToRemove === this.tail) { | |
| this.removeTail(); | |
| } else { | |
| const nextNode = nodeToRemove.getNextNode(); | |
| const previousNode = nodeToRemove.getPreviousNode(); | |
| nextNode.setPreviousNode(previousNode); | |
| previousNode.setNextNode(nextNode); | |
| } | |
| return nodeToRemove; | |
| } | |
| printList() { | |
| let currentNode = this.head; | |
| let output = '<head> '; | |
| while (currentNode !== null) { | |
| output += currentNode.data + ' '; | |
| currentNode = currentNode.getNextNode(); | |
| } | |
| output += '<tail>'; | |
| console.log(output); | |
| } | |
| } | |
| const subway = new DoublyLinkedList() | |
| module.exports = DoublyLinkedList; |
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