Java Program for Clockwise rotation of Linked List

// Java implementation of the approach
class GFG
{
    
/* Link list node */
static class Node
{
    int data;
    Node next;
}

/* A utility function to push a node */
static Node push(Node head_ref, int new_data)
{
    /* allocate node */
    Node new_node = new Node();

    /* put in the data */
    new_node.data = new_data;

    /* link the old list off the new node */
    new_node.next = (head_ref);

    /* move the head to point to the new node */
    (head_ref) = new_node;
    return head_ref;
}

/* A utility function to print linked list */
static void printList(Node node)
{
    while (node != null)
    {
        System.out.print(node.data + " -> ");
        node = node.next;
    }
    System.out.print( "null");
}

// Function that rotates the given linked list
// clockwise by k and returns the updated
// head pointer
static Node rightRotate(Node head, int k)
{

    // If the linked list is empty
    if (head == null)
        return head;

    // len is used to store length of the linked list
    // tmp will point to the last node after this loop
    Node tmp = head;
    int len = 1;
    while (tmp.next != null)
    {
        tmp = tmp.next;
        len++;
    }

    // If k is greater than the size
    // of the linked list
    if (k > len)
        k = k % len;

    // Subtract from length to convert
    // it into left rotation
    k = len - k;

    // If no rotation needed then
    // return the head node    
    if (k == 0 || k == len)
        return head;

    // current will either point to
    // kth or null after this loop
    Node current = head;
    int cnt = 1;
    while (cnt < k && current != null)
    {
        current = current.next;
        cnt++;
    }

    // If current is null then k is equal to the
    // count of nodes in the list
    // Don't change the list in this case
    if (current == null)
        return head;

    // current points to the kth node
    Node kthnode = current;

    // Change next of last node to previous head
    tmp.next = head;

    // Change head to (k+1)th node
    head = kthnode.next;

    // Change next of kth node to null
    kthnode.next = null;

    // Return the updated head pointer
    return head;
}

// Driver code
public static void main(String args[])
{

    /* The constructed linked list is: 
    1.2.3.4.5 */
    Node head = null;
    head = push(head, 5);
    head = push(head, 4);
    head = push(head, 3);
    head = push(head, 2);
    head = push(head, 1);

    int k = 2;

    // Rotate the linked list
    Node updated_head = rightRotate(head, k);

    // Print the rotated linked list
    printList(updated_head);
}
}

// This code is contributed by Arnub Kundu