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Rotate Linked List block wise
  • Difficulty Level : Medium
  • Last Updated : 18 Jan, 2021
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Given a Linked List of length n and block length k rotate in 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. 

C++




// C++ program to rotate a linked list block wise
#include<bits/stdc++.h>
using namespace std;
 
/* Link list node */
class Node
{
    public:
    int data;
    Node* next;
};
 
// Recursive function to rotate one block
Node* rotateHelper(Node* blockHead,
                        Node* blockTail,
                        int d, Node** tail,
                        int k)
{
    if (d == 0)
        return blockHead;
 
    // Rotate Clockwise
    if (d > 0)
    {
        Node* temp = blockHead;
        for (int i = 1; temp->next->next &&
                        i < k - 1; i++)
            temp = temp->next;
        blockTail->next = blockHead;
        *tail = temp;
        return rotateHelper(blockTail, temp,
                            d - 1, tail, k);
    }
 
    // Rotate anti-Clockwise
    if (d < 0)
    {
        blockTail->next = blockHead;
        *tail = blockHead;
        return rotateHelper(blockHead->next,
                blockHead, d + 1, tail, k);
    }
}
 
// Function to rotate the linked list block wise
Node* rotateByBlocks(Node* head,
                                int k, int d)
{
    // If length is 0 or 1 return head
    if (!head || !head->next)
        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 && 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,
                                    &tail, i);
    else
        head = rotateHelper(head, temp, d % k,
                                    &tail, 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 */
void 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;
}
 
/* Function to print linked list */
void printList(Node* node)
{
    while (node != NULL)
    {
        cout << node->data << " ";
        node = node->next;
    }
}
 
/* Driver code*/
int main()
{
    /* 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)
        push(&head, i);
 
    cout<<"Given linked list \n";
    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);
 
    cout << "\nRotated by blocks Linked list \n";
    printList(head);
 
    return (0);
}
 
// This is code is contributed by rathbhupendra

C




// C program to rotate a linked list block wise
#include <stdio.h>
#include <stdlib.h>
 
/* Link list node */
struct Node {
    int data;
    struct Node* next;
};
 
// Recursive function to rotate one block
struct Node* rotateHelper(struct Node* blockHead,
                          struct Node* blockTail,
                          int d, struct Node** tail,
                          int k)
{
    if (d == 0)
        return blockHead;
 
    // Rotate Clockwise
    if (d > 0) {
        struct Node* temp = blockHead;
        for (int i = 1; temp->next->next &&
                        i < k - 1; i++)
            temp = temp->next;
        blockTail->next = blockHead;
        *tail = temp;
        return rotateHelper(blockTail, temp,
                            d - 1, tail, k);
    }
 
    // Rotate anti-Clockwise
    if (d < 0) {
        blockTail->next = blockHead;
        *tail = blockHead;
        return rotateHelper(blockHead->next,
                blockHead, d + 1, tail, k);
    }
}
 
// Function to rotate the linked list block wise
struct Node* rotateByBlocks(struct Node* head,
                                 int k, int d)
{
    // If length is 0 or 1 return head
    if (!head || !head->next)
        return head;
 
    // if degree of rotation is 0, return head
    if (d == 0)
        return head;
 
    struct Node* temp = head, *tail = NULL;
 
    // Traverse upto last element of this block
    int i;
    for (i = 1; temp->next && i < k; i++)
        temp = temp->next;
 
    // storing the first node of next block
    struct 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,
                                    &tail, i);
    else
        head = rotateHelper(head, temp, d % k,
                                    &tail, 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 */
void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node = new Node;
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}
 
/* Function to print linked list */
void printList(struct Node* node)
{
    while (node != NULL) {
        printf("%d ", node->data);
        node = node->next;
    }
}
 
/* Driver program to test above function*/
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
 
    // create a list 1->2->3->4->5->
    // 6->7->8->9->NULL
    for (int i = 9; i > 0; i -= 1)
        push(&head, i);
 
    printf("Given linked list \n");
    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);
 
    printf("\nRotated by blocks Linked list \n");
    printList(head);
 
    return (0);
}

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 code*/
public 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 \n");
    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("\nRotated by blocks Linked list \n");
    printList(head);
}
}
 
// This code contributed by aashish1995

Python3




# Python3 program to rotate a linked
# list block wise
 
# Link list node
class Node:   
    def __init__(self, data):     
        self.data = data
        self.next = None
 
# Recursive function to rotate one block
def rotateHelper(blockHead, blockTail,
                 d, tail, k):   
    if (d == 0):
        return blockHead, tail
  
    # Rotate Clockwise
    if (d > 0):
        temp = blockHead
        i = 1       
        while temp.next.next != None and i < k - 1:
            temp = temp.next
            i += 1           
        blockTail.next = blockHead
        tail = temp
        return rotateHelper(blockTail, temp,
                            d - 1, tail, k)
 
    # Rotate anti-Clockwise
    if (d < 0):
        blockTail.next = blockHead
        tail = blockHead
        return rotateHelper(blockHead.next,
                            blockHead, d + 1,
                            tail, k)
     
# Function to rotate the linked list block wise
def rotateByBlocks(head, k, d):
 
    # If length is 0 or 1 return head
    if (head == None or head.next == None):
        return head
  
    # If degree of rotation is 0, return head
    if (d == 0):
        return head
    temp = head
    tail = None
  
    # Traverse upto last element of this block
    i = 1   
    while temp.next != None and i < k:
        temp = temp.next
        i += 1
  
    # Storing the first node of next block
    nextBlock = temp.next
  
    # If nodes of this block are less than k.
    # Rotate this block also
    if (i < k):
        head, tail = rotateHelper(head, temp, d % k,
                                  tail, i)
    else:
        head, tail = rotateHelper(head, temp, d % k,
                                  tail, 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
def push(head_ref, new_data):
 
    new_node = Node(new_data)
    new_node.data = new_data
    new_node.next = (head_ref)
    (head_ref) = new_node
    return head_ref
 
# Function to print linked list
def printList(node):
    while (node != None):
        print(node.data, end = ' ')
        node = node.next
     
# Driver code
if __name__=='__main__':
     
    # Start with the empty list
    head = None
  
    # Create a list 1.2.3.4.5.
    # 6.7.8.9.None
    for  i in range(9, 0, -1):
        head = push(head, i)
    print("Given linked list ")
    printList(head)
  
    # k is block size and d is number of
    # rotations in every block.
    k = 3
    d = 2
    head = rotateByBlocks(head, k, d)
  
    print("\nRotated by blocks Linked list ")
    printList(head)
  
# This code is contributed by rutvik_56

C#




// C# program to rotate a linked list block wise
using System;
public class GFG
{
 
  /* Link list node */
  public
    class Node
    {
      public
        int data;
      public
        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)
    {
      Console.Write(node.data + " ");
      node = node.next;
    }
  }
 
  /* Driver code*/
  public 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);
    Console.Write("Given linked list \n");
    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);
    Console.Write("\nRotated by blocks Linked list \n");
    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

This article is contributed by Chhavi. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

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