Javascript Program For Cloning A Linked List With Next And Random Pointer- Set 2

We have already discussed 2 different ways to clone a linked list. In this post, one more simple method to clone a linked list is discussed.

The idea is to use Hashing. Below is algorithm. 

1. Traverse the original linked list and make a copy in terms of data.
2. Make a hash map of key value pair with original linked list node and copied linked list node.
3. Traverse the original linked list again and using the hash map adjust the next and random reference of cloned linked list nodes.

Below is the implementation of above approach.

Javascript

<script>
// JavaScript program to clone a linked
// list with random pointers

// Linked List Node class
class Node
{
    constructor(data)
    {
        this.data = data;
        this.next = this.random = null;
    }
}

class LinkedList
{
    // Linked list constructor
    constructor(head)
    {
        this.head = head;
    }

    // Push method to put data always
    // at the head in the linked list.
    push(data)
    {
        let node = new Node(data);
        node.next = this.head;
        this.head = node;
    }

    // Method to print the list.
    print()
    {
        let temp = this.head;
        while (temp != null)
        {
            let random = temp.random;
            let randomData = ((random != null) ?
                               random.data : -1);
            document.write("Data = " + temp.data +
                           ", Random data = " +
                           randomData + "<br>");
            temp = temp.next;
        }
    }

    // Actual clone method which returns head
    // reference of cloned linked list.
    clone()
    {
        // Initialize two references, one with
        // original list's head.
        let origCurr = this.head,
            cloneCurr = null;

        // Hash map which contains node to node
        // mapping of original and clone linked list.
        let map = new Map();

        // Traverse the original list and make a
        // copy of that in the clone linked list.
        while (origCurr != null)
        {
            cloneCurr = new Node(origCurr.data);
            map.set(origCurr, cloneCurr);
            origCurr = origCurr.next;
        }

        // Adjusting the original list reference
        // again.
        origCurr = this.head;

        // Traversal of original list again to
        // adjust the next and random references
        // of clone list using hash map.
        while (origCurr != null)
        {
            cloneCurr = map.get(origCurr);
            cloneCurr.next = map.get(origCurr.next);
            cloneCurr.random = map.get(origCurr.random);
            origCurr = origCurr.next;
        }

        // Return the head reference of the
        // clone list.
        return new LinkedList(map.get(this.head));
    }
}

// Driver code
// Pushing data in the linked list.
let list =
new LinkedList(new Node(5));
list.push(4);
list.push(3);
list.push(2);
list.push(1);

// Setting up random references.
list.head.random =
list.head.next.next;
list.head.next.random =
list.head.next.next.next;
list.head.next.next.random =
list.head.next.next.next.next;
list.head.next.next.next.random =
list.head.next.next.next.next.next;
list.head.next.next.next.next.random =
list.head.next;

// Making a clone of the original
// linked list.
let clone = list.clone();

// Print the original and cloned
// linked list.
document.write(
"Original linked list<br>");
list.print();
document.write(
"<br>Cloned linked list<br>");
clone.print();
// This code is contributed by avanitrachhadiya2155
</script>

Output:

Original linked list
Data = 1, Random data = 3
Data = 2, Random data = 4
Data = 3, Random data = 5
Data = 4, Random data = -1
Data = 5, Random data = 2

Cloned linked list
Data = 1, Random data = 3
Data = 2, Random data = 4
Data = 3, Random data = 5
Data = 4, Random data = -1
Data = 5, Random data = 2

Time complexity: O(n) 
Auxiliary space: O(n)
Please refer complete article on Clone a linked list with next and random pointer | Set 2 for more details!