Javascript Program For Merging Two Sorted Linked Lists Such That Merged List Is In Reverse Order

// Javascript program to merge two 
// sorted linked list such that merged 
// list is in reverse order

// Node Class 
class Node {
    constructor(d) {
        this.data = d;
        this.next = null;
    }
}

// Head of list
let head;
let a, b;

function printlist(node) {
    while (node != null) {
        console.log (node.data );
        node = node.next;
    }
}

function sortedmerge(node1, node2) {
    // If both the nodes are null
    if (node1 == null && node2 == null) {
        return null;
    }

    // Resultant node
    let res = null;

    // If both of them have nodes
    //  present traverse them
    while (node1 != null &&
        node2 != null) {
        // Now compare both nodes 
        // current data
        if (node1.data <= node2.data) {
            let temp = node1.next;
            node1.next = res;
            res = node1;
            node1 = temp;
        }
        else {
            let temp = node2.next;
            node2.next = res;
            res = node2;
            node2 = temp;
        }
    }

    // If second list reached end, but
    // first list has nodes. Add 
    // remaining nodes of first
    // list at the front of result list
    while (node1 != null) {
        let temp = node1.next;
        node1.next = res;
        res = node1;
        node1 = temp;
    }

    // If first list reached end, but
    // second list has node. Add 
    // remaining nodes of first 
    // list at the front of result list
    while (node2 != null) {
        let temp = node2.next;
        node2.next = res;
        res = node2;
        node2 = temp;
    }
    return res;
}

// Driver code
let result = null;

/*Let us create two sorted linked lists 
  to test the above functions. Created 
  lists shall be
  a: 5->10->15
  b: 2->3->20*/
a = new Node(5);
a.next = new Node(10);
a.next.next = new Node(15);

b = new Node(2);
b.next = new Node(3);
b.next.next = new Node(20);

console.log ("List a before merge :");
printlist(a);
console.log ("List b before merge :");
printlist(b);

// Merge two sorted linkedlist in 
// decreasing order
result = sortedmerge(a, b);
console.log ("Merged linked list :");
printlist(result);
// This code is contributed by rag2127