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doublyLinkedList.js
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doublyLinkedList.js
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class Node{
constructor(val){
this.val = val;
this.next = null;
this.prev = null;
}
}
class DoublyLinkedList{
constructor(){
this.head = null;
this.tail = null;
this.length = 0;
}
// adding nodes at the end of doubly linked list
push(val){
let newNode = new Node(val);
if(!this.head || this.length === 0){
this.head = newNode;
this.tail = newNode;
} else{
this.tail.next = newNode;
newNode.prev = this.tail;
this.tail = newNode;
}
this.length++;
return this;
}
// removing a node from the end of doubly linked list
pop(){
if(!this.head || !this.tail || this.length === 0) return undefined;
let removeTail = this.tail;
if(this.length === 1){
this.head = null;
this.tail = null;
} else{
this.tail = removeTail.prev;
this.tail.next = null;
removeTail.prev = null;
}
this.length--;
return(removeTail);
}
unshifting(val){
let newNode = new Node(val);
if(!this.head){
this.head = newNode;
this.tail = newNode;
} else {
this.head.prev = newNode;
newNode.next = this.head;
this.head = newNode;
}
this.length++;
return this;
}
shift(){
if(!this.head) return undefinded;
if(this.length === 1){
this.head = null;
this.tail = null;
} else{
var shiftingNode = this.head;
this.head = this.head.next;
this.head.prev = null;
shiftingNode.next = null;
}
this.length--;
return(shiftingNode);
}
// accessing a node in a doubly linked list by its position
get(index){
if (index < 0 || index >= this.length ) return undefined;
let current, count;
if (index < this.length / 2){
count = 0;
current = this.head;
while(index !== count){
current = current.next;
count++;
}
} else {
count = this.length - 1;
current = this.tail;
while(index !== count){
current = current.prev;
count--;
}
}
return(current);
}
// set - replacing the value of a node in a doubly linked list
set(index, val){
let foundNode = this.get(index);
if(foundNode !== null){
foundNode.next = next;
return true;
}
return false;
}
// adding a node in doubly linked list in a certain index
insert(index, val){
if(index < 0 || index > this.length) return undefined;
if(index === 0) return !!this.unshifting(val);
if(index === this.length) return !!this.push(val);
let newNode = new Node(val);
let beforeNode = this.get(index-1);
let afterNode = beforeNode.next;
beforeNode.next = newNode;
newNode.prev = beforeNode;
afterNode.prev = newNode;
newNode.next = afterNode;
this.length++;
console.log(true);
}
// removing a node in a doubly linked list by a certain position
remove(index){
if(index < 0 || index >= this.length ) return undefined;
if(index === 0 ) return this.shift(index);
if(index === this.length - 1) return this.pop(index);
let removedNode = this.get(index);
let beforeNode = removedNode.prev;
let afterNode = removedNode.after;
beforeNode.next = afterNode;
afterNode.prev = beforeNode;
// removedNode.prev.next = removedNode.next;
// removedNode.next.prev = removedNode.prev;
removedNode.prev = null;
removedNode.next = null;
this.length--;
return removedNode;
}
}
let list = new DoublyLinkedList();
list.push('first');
list.push('second');
list.push('third');
list.remove(1);
console.log(list);