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Python3 Program to Count rotations in sorted and rotated linked list

  • Last Updated : 13 Jan, 2022

Given a linked list of n nodes which is first sorted, then rotated by k elements. Find the value of k.

The idea is to traverse singly linked list to check condition whether current node value is greater than value of next node. If the given condition is true, then break the loop. Otherwise increase the counter variable and increase the node by node->next. Below is the implementation of this approach.

Python3




# Program for count number of rotations in
# sorted linked list.
  
# Linked list node 
class Node:
      
    def __init__(self, data):
          
        self.data = data
        self.next = None
  
# Function that count number of
# rotation in singly linked list.
def countRotation(head):
  
    # Declare count variable and assign it 1.
    count = 0
   
    # Declare a min variable and assign to
    # data of head node.
    min = head.data
   
    # Check that while head not equal to None.
    while (head != None):
   
        # If min value is greater then head->data
        # then it breaks the while loop and
        # return the value of count.
        if (min > head.data):
            break
   
        count += 1
   
        # head assign the next value of head.
        head = head.next
      
    return count
  
# Function to push element in linked list.
def push(head, data):
  
    # Allocate dynamic memory for newNode.
    newNode = Node(data)
   
    # Assign the data into newNode.
    newNode.data = data
   
    # newNode->next assign the address of
    # head node.
    newNode.next = (head)
   
    # newNode become the headNode.
    (head) = newNode
    return head
  
# Display linked list.
def printList(node):
  
    while (node != None):
        print(node.data, end = ' ')
        node = node.next
      
# Driver code
if __name__=='__main__':
      
    # Create a node and initialize with None
    head = None
   
    # push() insert node in linked list.
    # 15 -> 18 -> 5 -> 8 -> 11 -> 12
    head = push(head, 12)
    head = push(head, 11)
    head = push(head, 8)
    head = push(head, 5)
    head = push(head, 18)
    head = push(head, 15)
   
    printList(head);
    print()
    print("Linked list rotated elements: "
          end = '')
   
    # Function call countRotation()
    print(countRotation(head))
  
# This code is contributed by rutvik_56

 
 

Output
15 18 5 8 11 12 
Linked list rotated elements: 2

 

Please refer complete article on Count rotations in sorted and rotated linked list for more details!


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