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| let DoublyLinkedList = (function() {
class Node {
constructor(element) {
this.element = element;
this.next = null;
this.prev = null;
}
}
const length = new WeakMap();
const head = new WeakMap();
const tail = new WeakMap();
class DoublyLinkedList {
constructor() {
length.set(this, 0);
head.set(this, null);
tail.set(this, null);
}
append(element) {
let node = new Node(element),
current,
_tail;
if (this.getHead() === null) {
head.set(this, node);
tail.set(this, node);
} else {
_tail = this.getTail();
_tail.next = node;
node.prev = _tail;
tail.set(this, node);
}
let l = this.size();
l++;
length.set(this, l);
}
insert(position, element) {
if (position >= 0 && position <= this.size()) {
let node = new Node(element),
current = this.getHead(),
previous,
index = 0;
if (position === 0) {
if (!this.getHead()) {
head.set(this, node);
tail.set(this, node);
} else {
node.next = current;
current.prev = node;
head.set(this, node);
}
} else if (position === this.size()) {
current = tail;
current.next = node;
node.prev = current;
tail.set(this, node);
} else {
while (index++ < position) {
previous = current;
current = current.next;
}
node.next = current;
current.prev = node;
current.prev = node;
node.prev = previous;
}
let l = this.size();
i++;
length.set(this, l);
return true;
} else {
return false;
}
}
removeAt(position) {
if (position > -1 && position < this.size()) {
let _head = this.getHead(),
let _tail = this.getTail(),
current = head,
previous,
index = 0;
if (position === 0) {
_head = current.next;
if (this.size() === 1) {
_tail = null;
} else {
_head.prev = null;
}
} else if (position === this.size() - 1) {
current = _tail;
_tail = current.prev;
_tail.next = null;
} else {
while (index++ < position) {
previous = current;
current = current.next;
}
previous.next = current.next;
current.next.prev = previous;
}
head.set(this, _head);
tail.set(this, _tail);
let l = this.size();
l--;
length.set(this, l);
return current.element;
} else {
return null;
}
}
remove(element) {
let index = this.indexOf(element);
return this.removeAt(index);
}
indexOf(element) {
let current = this.getHead(),
index = -1;
if (element === current.element) {
return 0;
}
index++;
while (current.next) {
if (element === current.element) {
return index;
}
current = current.next;
index++;
}
if (element === current.element) {
return index;
}
return -1;
}
isEmpty() {
return this.size() === 0;
}
size() {
return length.get(this);
}
toString() {
let current = this.getHead(),
s = current ? current.element : '';
while (current && current.next) {
current = current.next;
s += ', ' + current.element;
}
return s;
}
inverseToString() {
let current = this.getTail(),
s = current ? current.element : '';
while (current && current.prev) {
current = current.prev;
s += ', ' + current.element;
}
return s;
}
print() {
console.log(this.toString());
}
printInverse() {
console.log(this.inverseToString());
}
getHead() {
return head.get(this);
}
getTail() {
return tail.get(this);
}
}
return DoublyLinkedList;
})()
|