Rotate Doubly Linked List Java

PROGRAM TO ROTATE DOUBLY LINKED LIST BY N NODES

class LinkedList { 

  

/* Link list node */

static class Node

{ 

    char data; 

    Node prev; 

    Node next; 

}

static Node head = null;

  

// This function rotates a doubly linked 

// list counter-clockwise and updates the 

// head. The function assumes that N is 

// smallerthan size of linked list. It 

// doesn't modify the list if N is greater 

// than or equal to size 

static void rotate( int N) 

{ 

    if (N == 0) 

        return; 

  

    // Let us understand the below code 

    // for example N = 2 and 

    // list = a <-> b <-> c <-> d <-> e. 

    Node current = head; 

  

    // current will either point to Nth 

    // or NULL after this loop. Current 

    // will point to node 'b' in the 

    // above example 

    int count = 1; 

    while (count < N && current != null)

    { 

        current = current.next; 

        count++; 

    } 

  

    // If current is NULL, N 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 Nth node. Store 

    // it in a variable. NthNode points to 

    // node 'b' in the above example 

    Node NthNode = current; 

  

    // current will point to last node 

    // after this loop current will point 

    // to node 'e' in the above example 

    while (current.next != null) 

        current = current.next; 

  

    // Change next of last node to previous 

    // head. Next of 'e' is now changed to 

    // node 'a' 

    current.next = head; 

  

    // Change prev of Head node to current 

    // Prev of 'a' is now changed to node 'e' 

    (head).prev = current; 

  

    // Change head to (N+1)th node 

    // head is now changed to node 'c' 

    head = NthNode.next; 

  

    // Change prev of New Head node to NULL 

    // Because Prev of Head Node in Doubly 

    // linked list is NULL 

    (head).prev = null; 

  

    // change next of Nth node to NULL 

    // next of 'b' is now NULL 

    NthNode.next = null; 

} 

  

// Function to insert a node at the 

// beginning of the Doubly Linked List 

static void push(char new_data) 

{ 

    Node new_node = new Node(); 

    new_node.data = new_data; 

    new_node.prev = null; 

    new_node.next = (head); 

    if ((head) != null) 

        (head).prev = new_node; 

head = new_node; 

} 

  

/* Function to print linked list */

static void printList(Node node) 

{ 

    while (node != null && node.next != null)

    { 

        System.out.print(node.data + " "); 

        node = node.next; 

    } 

    if(node != null)

    System.out.print(node.data); 

} 

  

// Driver's Code 

public static void main(String[] args) 

{ 

    /* Start with the empty list */

    // Node head = null; 

  

    /* Let us create the doubly 

    linked list a<->b<->c<->d<->e */

    push( 'e'); 

    push( 'd'); 

    push('c'); 

    push('b'); 

    push( 'a'); 

  

    int N = 2; 

  

    System.out.println("Given linked list "); 

    printList(head); 

    rotate( N); 

    System.out.println();

    System.out.println("Rotated Linked list "); 

    printList(head); 

} 

} 

OUTPUT:

Given linked list 
a  b  c  d  e
Rotated Linked list 
c  d  e  a  b

CREDITS: https://www.geeksforgeeks.org/rotate-doubly-linked-list-n-nodes/