JavaScript Program to Copy all Nodes of a Linked List

In JavaScript, copying all nodes of a linked list can be done by creating a duplicate of the entire linked list by maintaining the structure of each element. We can copy all nodes using Recursion and Map.

Using Recursion

In this approach, we use a recursive function recursiveFn to traverse the original linked list and create a new linked list with copied nodes. The recursion continues till the entire original linked list is traversed, which results in a deep copy of the original linked list.

Example: The example below uses Recursion to copy all linked list nodes.

Javascript

class Node {
    constructor(data) {
        this.data = data;
        this.next = null;
    }
}
let head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
let original = head;
console.log("Original Nodes: ")
while (original) {
    process.stdout.write
    (original.data.toString());
    original = original.next;
    if (original) {
        process.stdout.write(" -> ");
    }
}
console.log();
function recursiveFn(oNode) {
    if (!oNode) return null;
    let temp = new Node(oNode.data);
    temp.next =
        recursiveFn(oNode.next);
    return temp;
}
let cTemp = recursiveFn(head);
let cTemp2 = cTemp;
console.log("Copied Nodes: ")
while (cTemp2) {
    process.stdout.write
    (cTemp2.data.toString());
    cTemp2 = cTemp2.next;
    if (cTemp2) {
        process.stdout.write(" -> ");
    }
}
console.log();

Output

Original Nodes: 
1 -> 2 -> 3 -> 4 -> 5
Copied Nodes: 
1 -> 2 -> 3 -> 4 -> 5

Using Map

In this approach, a new linked list is created by iterating through the original linked list and also using a Map to associate each node in the original list with its corresponding copied node. This Map is then uses to link the copied nodes and create a deep copy of the original linked list.

Syntax:

let myMap = new Map();

Example: The example below uses a Map to copy all linked list nodes.

Javascript

class Node {
    constructor(data) {
        this.data = data;
        this.next = null;
    }
}
let head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
let curr = head;
console.log("Original Node: ")
while (curr) {
    process.stdout.write
    (curr.data.toString());
    curr = curr.next;
    if (curr) {
        process.stdout.write(" -> ");
    }
}
console.log();
let copyHead = new Node(head.data);
let map = new Map([[head, copyHead]]);
let temp1 = head.next;
let temp2 = copyHead;
while (temp1) {
    temp2.next = new Node(temp1.data);
    temp2 = temp2.next;
    map.set(temp1, temp2);
    temp1 = temp1.next;
}
temp1 = head;
temp2 = copyHead;
while (temp1) {
    if (temp1.next) {
        temp2.next = map.get(temp1.next);
    }
    temp1 = temp1.next;
    temp2 = temp2.next;
}
let temp3 = copyHead;
console.log("Copied Node: ")
while (temp3) {
    process.stdout.write
    (temp3.data.toString());
    temp3 = temp3.next;
    if (temp3) {
        process.stdout.write(" -> ");
    }
}
console.log();

Output

Original Node: 
1 -> 2 -> 3 -> 4 -> 5
Copied Node: 
1 -> 2 -> 3 -> 4 -> 5