Javascript Program For Rotating A Linked List

// Javascript program to rotate
// a linked list

// Head of list
let head;

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

// This function rotates a linked list 
// counter-clockwise and updates the head. 
// The function assumes that k is smaller 
// than size of linked list. It doesn't 
// modify the list if k is greater than 
// or equal to size
function rotate(k) {
    if (k == 0)
        return;

    // Let us understand the below code 
    // for example k = 4 and list = 
    // 10->20->30->40->50->60.
    let current = head;

    // current will either point to kth or 
    // NULL after this loop. current will 
    // point to node 40 in the above example
    let count = 1;

    while (count < k && current != null) {
        current = current.next;
        count++;
    }

    // If current is NULL, k is greater than 
    // or equal to count of nodes in linked list. 
    // Don't change the list in this case
    if (current == null)
        return;

    // current points to kth node. Store it in 
    // a letiable. kthNode points to node 40 
    // in the above example
    let kthNode = current;

    // current will point to last node after 
    // this loop current will point to node 
    // 60 in the above example
    while (current.next != null)
        current = current.next;

    // Change next of last node to previous 
    // head Next of 60 is now changed to 
    // node 10
    current.next = head;

    // Change head to (k+1)th node
    // head is now changed to node 50
    head = kthNode.next;

    // change next of kth node to null
    kthNode.next = null;
}

/* Given a reference (pointer to pointer) to 
   the head of a list and an int, push
   a new node on the front of the list. */
function push(new_data) {

    /* 1 & 2: Allocate the Node &
        Put in the data */
    let new_node = new Node(new_data);

    // 3. Make next of new Node as head 
    new_node.next = head;

    // 4. Move the head to point to new Node 
    head = new_node;
}

function printList() {
    let temp = head;
    while (temp != null) {
        console.log(temp.data + " ");
        temp = temp.next;
    }
}

// Driver code
// Create a list 
// 10->20->30->40->50->60
for (i = 60; i >= 10; i -= 10)
    push(i);

console.log("Given list<br />");
printList();

rotate(4);

console.log("Rotated Linked List<br />");
printList();

<script>
// Javascript program to rotate
// a linked list counter clock wise

// Link list node 
class Node 
{
    constructor() 
    {
        this.data = 0;
        this.next = null;
    }
}

var head = null;

// This function rotates a linked list
// counter-clockwise and updates the
// head. The function assumes that k is
// smaller than size of linked list.
function rotate(k) 
{
    if (k == 0)
        return;

    // Let us understand the below
    // code for example k = 4 and
    // list = 10.20.30.40.50.60.
    var current = head;

    // Traverse till the end.
    while (current.next != null)
        current = current.next;

    current.next = head;
    current = head;

    // Traverse the linked list to 
    // k-1 position which will be 
    // last element for rotated array.
    for (i = 0; i < k - 1; i++)
        current = current.next;

    // update the head_ref and last 
    // element pointer to null
    head = current.next;
    current.next = null;
}

// UTILITY FUNCTIONS 
// Function to push a node 
function push(new_data) 
{
    // Allocate node 
    var new_node = new Node();

    // Put in the data 
    new_node.data = new_data;

    // Link the old list of the 
    // new node 
    new_node.next = head;

    // Move the head to point to the 
    // new node 
    head = new_node;
}

// Function to print linked list 
function printList( node) 
{
    while (node != null) 
    {
        document.write(node.data + " ");
        node = node.next;
    }
}

// Driver code 
// Start with the empty list 
// Create a list 10.20.30.40.50.60
for (i = 60; i > 0; i -= 10)
    push(i);

document.write("Given linked list <br/>");
printList(head);
rotate(4);

document.write("<br/>Rotated Linked list <br/>");
printList(head);
// This code is contributed by aashish1995
</script>