|
| 1 | +const Node = require('./Node'); |
| 2 | + |
| 3 | +class LinkedList { |
| 4 | + constructor() { |
| 5 | + this.head = null; |
| 6 | + } |
| 7 | + |
| 8 | + addToHead(data) { |
| 9 | + const newHead = new Node(data); |
| 10 | + const currentHead = this.head; |
| 11 | + this.head = newHead; |
| 12 | + if (currentHead) { |
| 13 | + this.head.setNextNode(currentHead); |
| 14 | + } |
| 15 | + } |
| 16 | + |
| 17 | + addToTail(data) { |
| 18 | + let tail = this.head; |
| 19 | + if (!tail) { |
| 20 | + this.head = new Node(data); |
| 21 | + } else { |
| 22 | + while (tail.getNextNode() !== null) { |
| 23 | + tail = tail.getNextNode(); |
| 24 | + } |
| 25 | + tail.setNextNode(new Node(data)); |
| 26 | + } |
| 27 | + } |
| 28 | + |
| 29 | + removeHead() { |
| 30 | + const removedHead = this.head; |
| 31 | + if (!removedHead) { |
| 32 | + return; |
| 33 | + } |
| 34 | + this.head = removedHead.getNextNode(); |
| 35 | + return removedHead.data; |
| 36 | + } |
| 37 | + |
| 38 | + printList(){ |
| 39 | + let currentNode = this.head; |
| 40 | + let output = '<head> '; |
| 41 | + while (currentNode !== null){ |
| 42 | + output += currentNode.data + ' '; |
| 43 | + currentNode = currentNode.getNextNode(); |
| 44 | + } |
| 45 | + output += '<tail>'; |
| 46 | + console.log(output); |
| 47 | + } |
| 48 | +} // end LinkedList class |
| 49 | + |
| 50 | + |
| 51 | + |
| 52 | +module.exports = LinkedList; |
| 53 | + |
| 54 | + |
| 55 | + |
| 56 | +/* |
| 57 | +A linked list is a sequential chain of nodes, each of which |
| 58 | +contains two elements: data and a link to the next node. |
| 59 | +Uses nodes from Node class in Node.js. |
| 60 | +
|
| 61 | +addToHead(data): |
| 62 | +takes one parameter called data. Inside the method, create |
| 63 | +a Node const variable named newHead, and pass data as an argument. |
| 64 | +It checks if there is a current head to the list. If there is, |
| 65 | +it set the list’s head’s next node to currentHead. |
| 66 | +
|
| 67 | +addToTail(data): |
| 68 | +takes one parameter called data and starts with a variable tail |
| 69 | +set equal to the list’s head. If there is no head, that means that |
| 70 | +the list is empty, and we will be creating the head and tail with |
| 71 | +the data passed in. Otherwise, we will iterate through the list until |
| 72 | +we find the last node (current tail) and we will add a pointer |
| 73 | +from that node to our new tail. |
| 74 | +
|
| 75 | +removeHead() |
| 76 | +takes no parameters. Sets variable removedHead to the list’s |
| 77 | +original head to keep track of it. It checks to see if the list |
| 78 | +had a head. If it doesn’t it returns nothing. If there is a head, |
| 79 | +it will remove it by setting the list’s head equal to the original |
| 80 | +head’s next node, and then return that original head data. |
| 81 | +
|
| 82 | +printList() |
| 83 | +creates a String (output) that holds the data from every node |
| 84 | +in the list starting at the list’s head set to variable currentNode. |
| 85 | +It iterates through the list adding currentNode's data and a ' ' to |
| 86 | +output and then updating currentNode to its next node. It does it |
| 87 | +while currentNode doesn’t equal null. |
| 88 | +*/ |
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