Given a Linked List of length n and block length k rotate in a circular manner towards right/left each block by a number d. If d is positive rotate towards right else rotate towards left.
Examples:
Input: 1->2->3->4->5->6->7->8->9->NULL,
k = 3
d = 1
Output: 3->1->2->6->4->5->9->7->8->NULL
Explanation: Here blocks of size 3 are
rotated towards right(as d is positive)
by 1.
Input: 1->2->3->4->5->6->7->8->9->10->
11->12->13->14->15->NULL,
k = 4
d = -1
Output: 2->3->4->1->6->7->8->5->10->11
->12->9->14->15->13->NULL
Explanation: Here, at the end of linked
list, remaining nodes are less than k, i.e.
only three nodes are left while k is 4.
Rotate those 3 nodes also by d.
Prerequisite: Rotate a linked list
The idea is if the absolute value of d is greater than the value of k, then rotate the link list by d % k times. If d is 0, no need to rotate the linked list at all.
Java
// Java program to rotate a linked list // block wise import java.util.*;class GFG{ // Link list node static class Node { int data; Node next; }; static Node tail; // Recursive function to rotate one block static Node rotateHelper(Node blockHead, Node blockTail, int d, int k) { if (d == 0) return blockHead; // Rotate Clockwise if (d > 0) { Node temp = blockHead; for (int i = 1; temp.next.next!=null && i < k - 1; i++) temp = temp.next; blockTail.next = blockHead; tail = temp; return rotateHelper(blockTail, temp, d - 1, k); } // Rotate anti-Clockwise if (d < 0) { blockTail.next = blockHead; tail = blockHead; return rotateHelper(blockHead.next, blockHead, d + 1, k); } return blockHead;} // Function to rotate the linked list // block-wise static Node rotateByBlocks(Node head, int k, int d) { // If length is 0 or 1 return head if (head == null || head.next == null) return head; // if degree of rotation is 0, // return head if (d == 0) return head; Node temp = head; tail = null; // Traverse upto last element of // this block int i; for (i = 1; temp.next != null && i < k; i++) temp = temp.next; // Storing the first node of next block Node nextBlock = temp.next; // If nodes of this block are less than k. // Rotate this block also if (i < k) head = rotateHelper(head, temp, d % k, i); else head = rotateHelper(head, temp, d % k, k); // Append the new head of next block to // the tail of this block tail.next = rotateByBlocks(nextBlock, k, d % k); // return head of updated Linked List return head; } // UTILITY FUNCTIONS // Function to push a node static Node push(Node head_ref, int new_data) { Node new_node = new Node(); new_node.data = new_data; new_node.next = head_ref; head_ref = new_node; return head_ref; } // Function to print linked list static void printList(Node node) { while (node != null) { System.out.print(node.data + " "); node = node.next; } } // Driver codepublic static void main(String[] args) { /* Start with the empty list */ Node head = null; // Create a list 1.2.3.4.5. // 6.7.8.9.null for (int i = 9; i > 0; i -= 1) head = push(head, i); System.out.print("Given linked list "); printList(head); // k is block size and d is number of // rotations in every block. int k = 3, d = 2; head = rotateByBlocks(head, k, d); System.out.print( "Rotated by blocks Linked list "); printList(head); }} // This code is contributed by aashish1995 |
Output:
Given linked list 1 2 3 4 5 6 7 8 9 Rotated by blocks Linked list 2 3 1 5 6 4 8 9 7
Please refer complete article on Rotate Linked List block wise for more details!
