Javascript Program For Pairwise Swapping Elements Of A Given Linked List By Changing Links

// Javascript program to swap elements 
// of linked list by changing links
let head;

class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}

/* Function to pairwise swap elements 
   of a linked list */
function pairWiseSwap(node) {
    // If linked list is empty or there 
    // is only one node in list
    if (node == null ||
        node.next == null) {
        return node;
    }

    // Initialize previous and current 
    // pointers
    let prev = node;
    let curr = node.next;

    // Change head before proceeding
    node = curr;

    // Traverse the list
    while (true) {
        let next = curr.next;

        // Change next of current as 
        // previous node
        curr.next = prev;

        // If next NULL or next is the 
        // last node
        if (next == null ||
            next.next == null) {
            prev.next = next;
            break;
        }

        // Change next of previous to next 
        // next
        prev.next = next.next;

        // Update previous and curr
        prev = next;
        curr = prev.next;
    }
    return node;
}

/* Function to print nodes in a 
   given linked list */
function printList(node) {
    while (node != null) {
        console.log(node.data + " ");
        node = node.next;
    }
}

// Driver code
/* The constructed linked list is: 
   1->2->3->4->5->6->7 */
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);
head.next.next.next.next.next =
    new Node(6);
head.next.next.next.next.next.next =
    new Node(7);

console.log("Linked list before calling pairwiseSwap() ");
printList(head);
let st = pairWiseSwap(head);
console.log("Linked list after calling pairwiseSwap() ");
printList(st);
console.log("");
// This code is contributed by aashish1995 

// Javascript program to swap elements of
// linked list by changing links
let head;
class Node 
{
    constructor(val) 
    {
        this.data = val;
        this.next = null;
    }
}

/* Function to pairwise swap elements of 
   a linked  It returns head of the modified 
   list, so return value of this node must be 
   assigned */
function pairWiseSwap(node) 
{
    // Base Case: The list is empty or has 
    // only one node
    if (node == null || 
        node.next == null) 
    {
        return node;
    }

// Store head of list after 
// two nodes
let remaining = node.next.next;

// Change head
let newhead = node.next;

// Change next of second node
node.next.next = node;

// Recur for remaining list and 
// change next of head
node.next = pairWiseSwap(remaining);

// Return new head of modified list
return newhead;
}

/* Function to print nodes in a 
   given linked list */
function printList(node) 
{
    while (node != null) 
    {
        console.log(node.data);
        node = node.next;
    }
}

// Driver code
/* The constructed linked list is: 
   1->2->3->4->5->6->7 */
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);
head.next.next.next.next.next = 
new Node(6);
head.next.next.next.next.next.next = 
new Node(7);

console.log("Linked list before calling pairwiseSwap() ");
printList(head);
head = pairWiseSwap(head);
console.log("Linked list after calling pairwiseSwap() ");
printList(head);
// This code is contributed by umadevi9616