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doubly-linked-list.js
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doubly-linked-list.js
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const ListEmpty = "ListEmpty";
class DoublyLinkedList {
constructor() {
this.head = null;
this.tail = null;
this.length = 0;
}
}
class Node {
constructor(data, next = null, prev = null) {
this.data = data;
this.next = next;
this.prev = prev;
}
}
const addLast = function(value) {
const node = new Node(value);
if (this.isEmpty()) {
this.head = node;
this.tail = node;
} else {
this.tail.next = node;
node.prev = this.tail;
this.tail = node;
}
this.length += 1;
};
const addFirst = function(value) {
const node = new Node(value);
if (this.isEmpty()) {
this.head = node;
this.tail = node;
} else {
this.head.prev = node;
node.next = this.head;
this.head = node;
}
this.length += 1;
};
const deleteLast = function() {
if (this.isEmpty()) {
throw ListEmpty;
} else if (this.length === 1){
this.head = null;
this.tail = null;
} else {
this.tail = this.tail.prev;
this.tail.next = null;
}
this.length -= 1;
};
const deleteFirst = function() {
if (this.isEmpty()) {
throw ListEmpty;
} else if (this.length === 1){
this.head = null;
this.tail = null;
} else {
this.head.next.prev = null;
this.head = this.head.next;
}
this.length -= 1;
};
const isEmpty = function() {
return this.head === null && this.tail === null;
}
const getFirst = function() {
if (this.isEmpty()) throw ListEmpty;
return this.head.data;
}
const getLast = function() {
if (this.isEmpty()) throw ListEmpty;
return this.tail.data;
}
DoublyLinkedList.prototype.addLast = addLast;
DoublyLinkedList.prototype.addFirst = addFirst;
DoublyLinkedList.prototype.deleteLast = deleteLast;
DoublyLinkedList.prototype.deleteFirst = deleteFirst;
DoublyLinkedList.prototype.isEmpty = isEmpty;
module.exports = DoublyLinkedList;