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linked-list.ts
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linked-list.ts
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class Node {
element: any;
next: Node = null;
constructor(element: any) {
this.element = element;
}
}
/**
* A linked list data structure, where each node in the list contains a
* reference to the node after it.
*/
export default class LinkedList {
length = 0;
head: Node = null;
/** Adds a new element to the end of the list. */
add(element: any): void {
if (this.head) {
let currentNode: Node = this.head;
while (currentNode.next) {
currentNode = currentNode.next;
}
currentNode.next = new Node(element);
} else {
this.head = new Node(element);
}
this.length++;
}
/**
* Removes the first occurrence of a given element from the list (if
* possible).
*/
remove(element: any): void {
if (this.head) {
if (this.head.element === element) {
this.head = this.head.next;
this.length--;
} else {
// Search for element
let currentNode: Node = this.head.next;
let previousNode: Node = this.head;
while (currentNode) {
if (currentNode.element === element) {
// Link adjacent nodes to each other
previousNode.next = currentNode.next;
this.length--;
break;
}
previousNode = currentNode;
currentNode = currentNode.next;
}
}
}
}
/** Returns the current number of elements in the list. */
size(): number {
return this.length;
}
/** Returns whether or not the list is empty. */
isEmpty(): boolean {
return this.length === 0;
}
/** Clears the contents of the list. */
clear(): void {
this.head = null;
this.length = 0;
}
/**
* Returns the numerical index of the first occurrence of the given element in
* the list (or `-1` if the list does not contain this element).
*/
indexOf(element: any): number {
let index = 0;
let currentNode: Node = this.head;
while (currentNode) {
if (currentNode.element === element) {
return index;
}
currentNode = currentNode.next;
index++;
}
return -1;
}
/**
* Returns the element at the given index in the list (or `undefined` if the
* list has no such index).
*/
elementAt(index: number): any {
if (index < 0 || index >= this.length) {
return undefined;
} else {
let currentNode = this.head;
for (let i = 0; i < index; i++) {
currentNode = currentNode.next;
}
return currentNode.element;
}
}
/**
* Removes and returns the element at the given index from the list (or
* returns `null` if the list has no such index).
*/
removeAt(index: number): any {
if (index < 0 || index >= this.length) {
return null;
} else if (index === 0) {
const removed = this.head.element;
this.head = this.head.next;
this.length--;
return removed;
} else {
// Find nodes at and around index
let currentIndex = 1;
let previousNode = this.head;
let currentNode = this.head.next;
while (currentIndex < index) {
previousNode = currentNode;
currentNode = currentNode.next;
currentIndex++;
}
// Link adjacent nodes to each other
previousNode.next = currentNode.next;
this.length--;
return currentNode.element;
}
}
/**
* Inserts a given element at a given index in the list (or returns `false` if
* given an invalid index).
*/
addAt(index: number, element: any): false | void {
if (index < 0 || index > this.length) {
return false;
} else if (index === 0) {
let newNode = new Node(element);
newNode.next = this.head;
this.head = newNode;
this.length++;
} else {
// Find nodes at and around index
let currentIndex = 1;
let currentNode = this.head.next;
let previousNode = this.head;
while (currentIndex < index) {
previousNode = currentNode;
currentNode = currentNode.next;
currentIndex++;
}
// Add and link up
let newNode = new Node(element);
newNode.next = currentNode;
previousNode.next = newNode;
this.length++;
}
}
}