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JavaScript Program to Copy all Nodes of a Linked List

Last Updated : 04 Mar, 2024
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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.

Table of Content

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

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