Here is the interview question prompt, presented for reference.

Now that we've implemented a Linked List, let's start operating on it! Assume you have a Linked List implementation with this definition:

class LinkedList {
    constructor() {
        this.head = null;
        this.tail = null;
    }

    prepend(newVal) {
        const currentHead = this.head;
        const newNode = new Node(newVal);
        newNode.next = currentHead;
        this.head = newNode;

        if (!this.tail) {
            this.tail = newNode;
        }
    }

    append(newVal) {
        const newNode = new Node(newVal);
        if (!this.head) {
            this.head = newNode;
            this.tail = newNode;
        } else {
            this.tail.next = newNode;
            this.tail = newNode;
        }
    }
}

Can you write a method getUnion to find the union of two linked lists? A union of two sets includes everything in both sets.

So given 1 -> 2 -> 3 and 3 -> 4 -> 5, we'd get 1 -> 2 -> 3 -> 4 -> 5.

Constraints

• Length of both the linkedlist <= 1000
• The nodes will always contain integer values between -1000000000 and 1000000000
• Let m, n be the lengths of the two lists
• Expected time complexity : O(n*m)
• Expected space complexity : O(n+m)

You can see the full challenge with visuals at this link.