@figliolia/data-structures/dist/mjs/LinkedList.js

Efficient data structures for every day programming

class ListNode {
    value;
    previous = null;
    next = null;
    constructor(value, previous = null, next = null) {
        this.value = value;
        this.next = next;
        this.previous = previous;
    }
}
/**
 * Linked List
 *
 * A doubly linked list mimicking the interface of JavaScript arrays
 *
 * ```typescript
 * import { LinkedList } from "@figliolia/data-structures";
 *
 * const list = new LinkedList<number>();
 * list.push(1);
 * list.push(2);
 * list.push(3);
 * for(const item of list) {
 *   console.log(item); // 1, 2, 3
 * }
 * list.pop(); // 3 -> O(1)
 * list.shift() // 1 -> O(1)
 * list.push(3) // O(1)
 * list.unshift(1) // O(1)
 * ```
 */
export class LinkedList {
    size = 0;
    head = null;
    tail = null;
    constructor(...items) {
        for (const item of items) {
            this.push(item);
        }
    }
    push(item) {
        this.size++;
        const node = new ListNode(item);
        if (!this.head && !this.tail) {
            this.head = node;
            this.tail = node;
            return this.size;
        }
        this.tail.next = node;
        node.previous = this.tail;
        this.tail = node;
        return this.size;
    }
    unshift(item) {
        this.size++;
        const node = new ListNode(item);
        if (!this.head && !this.tail) {
            this.head = node;
            this.tail = node;
            return this.size;
        }
        this.head.previous = node;
        node.next = this.head;
        this.head = node;
        return this.size;
    }
    shift() {
        if (!this.head) {
            return;
        }
        this.size--;
        const node = this.head;
        if (this.head === this.tail) {
            this.head = null;
            this.tail = null;
            return node.value;
        }
        this.head = node.next;
        this.head.previous = null;
        return node.value;
    }
    pop() {
        if (!this.tail) {
            return;
        }
        this.size--;
        const node = this.tail;
        if (this.head === this.tail) {
            this.head = null;
            this.tail = null;
            return node.value;
        }
        this.tail = node.previous;
        this.tail.next = null;
        return node.value;
    }
    peekLeft() {
        return this.head?.value;
    }
    peekRight() {
        return this.tail?.value;
    }
    *[Symbol.iterator]() {
        let current = this.head;
        while (current) {
            yield current.value;
            current = current.next;
        }
    }
}