# 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( "Rotated by blocks Linked list ") printList(head) # This code is contributed by rutvik_56