@dibzthedibz/linked-list-library/index.js

Methods to act upon linked lists

class LinkedList {
    constructor() {
        this.head = null
        this.tail = null
        this.size = 0
    }
    //Inserts a new node at the head of the list.
    insertAtHead(data) {
        const newNode = new LinkedListNode(data, this.head)
        this.head = newNode
        if (this.tail === null) {
            this.tail = newNode
        }
        this.size++
    }
    //Inserts a new node at the tail of the list.
    insertAtTail(data) {
        const newNode = new LinkedListNode(data, null)
        if (this.tail !== null) {
            this.tail.next = newNode;
        }
        this.tail = newNode;
        if (this.head === null) {
            this.head = newNode
        }
        this.size++
    }
    //Inserts a new node at the specified position.
    insertInMiddle(data, position) {
        if (position <= 0) {
            this.insertAtHead(data);
            return
        }
        else if (position >= this.size) {
            this.insertAtTail(data)
            return
        }
        const prev = this.findNodeAt(position - 1);
        console.log(`Previous node at position ${position - 1}: ${JSON.stringify(prev)}`);
        const newNode = new LinkedListNode(data, prev.next);
        prev.next = newNode;
        this.size++;
        console.log(`Node ${data} inserted at position ${position}`);
    }
    //Finds and returns the node at the specified position.
    findNodeAt(position) {
        let current = this.head
        let index = 0
        while (current !== null && index < position) {
            current = current.next
            index++
        }
        if (current === null) {
            console.log(`Node not found at position ${position}`);
        } else {
            console.log(`Found node at position ${position}: ${JSON.stringify(current)}`);
        }

        return current;
    }
    //Converts an array to a linked list.
    arrayToList(arr) {
        for (let i = arr.length - 1; i >= 0; i--) {
            this.insertAtHead(arr[i]);
        }
        return this;
    }
    //Converts the linked list to an array.
    listToArray() {
        let result = [];
        let curr = this.head;
        while (curr !== null) {
            result.push(curr.value);
            curr = curr.next;
        }
        return result;
    }
    //Makes the list circular by pointing the tail to the node at the specified position.
    makeCircular(position) {
        const targetNode = this.findNodeAt(position);
        if (this.tail !== null && targetNode !== null) {
            this.tail.next = targetNode;
        } else {
            console.log(`unable to create circular reference at position ${position}`);
        }
    }
    //Checks if the list is circular and returns true or false.
    isCircular() {
        if (this.head === null) {
            return false;
        }
        let slow = this.head;
        let fast = this.head;
        while (fast !== null && fast.next !== null) {
            slow = slow.next;
            fast = fast.next.next;
            if (slow === fast) {
                return true;
            }
        }
        return false;
    }
}


class LinkedListNode {
    constructor(value, next) {
        this.value = value
        this.next = next
    }
}

module.exports = LinkedList