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singlyLikedList.ts
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singlyLikedList.ts
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class SinglyLinkedListNode<T> {
value: T;
next: SinglyLinkedListNode<T> | null;
constructor(value: T) {
this.value = value;
this.next = null;
}
}
class LinkedList<T> {
head: SinglyLinkedListNode<T>;
size: number;
constructor() {
this.head = null;
this.size = 0;
}
push(value: T): void {
const newNode = new SinglyLinkedListNode(value);
if (this.head === null) {
this.head = newNode;
} else {
let current = this.head;
// as long as the next node exist, we can traverse until we reach the head
while (current.next !== null) {
current = current.next;
}
// we have reach the end already, so we just extend it
current.next = newNode;
}
this.size++;
}
removeFirst(): T | null {
if (this.isEmpty()) return null;
const deletedHeadValue = this.head.value;
this.head = this.head.next;
this.size--;
return deletedHeadValue;
}
removeLast() {
if (this.isEmpty()) return null;
if (this.size === 1) {
const headNodeValue = this.head.value;
this.head = null;
this.size--;
return headNodeValue;
}
let current = this.head;
let previous;
while (current.next !== null) {
previous = current;
current = current.next;
}
previous.next = null;
this.size--;
return current.value;
}
getFirst() {
if (this.isEmpty) return null;
return this.head;
}
getLast() {
if (this.isEmpty) return null;
let current = this.head;
while (current.next !== null) {
current = current.next;
}
return current;
}
isEmpty() {
return this.head === null;
}
insertAt(index: number, value: T): string {
if (index > this.size) {
return "Index out of range";
}
if (this.isEmpty()) {
return null;
}
let current = this.head;
let nodeIdex = 0;
const newNode = new SinglyLinkedListNode(value);
if (index === 0) {
current.next = current;
current = newNode;
}
let previous;
// we will traverse untill we reach before the
while (nodeIdex < index) {
previous = current;
current = current.next;
nodeIdex++;
}
previous.next = newNode;
newNode.next = current;
}
print() {
const allNodes = [];
let current = this.head;
while (current.next !== null) {
allNodes.push(current.value);
current = current.next;
}
// the tail value
allNodes.push(current.value);
return allNodes;
}
}
const myLinkedList = new LinkedList<number>();
myLinkedList.push(1);
myLinkedList.push(2);
myLinkedList.push(3);
myLinkedList.push(4);
myLinkedList.push(5);
// myLinkedList.removeLast();
myLinkedList.insertAt(3, 7);
const allNodes = myLinkedList.print();
console.log(allNodes);