Circular Linked List Python

PROGRAM TO CHECK IF A LINKED LIST IS CIRCULAR LINKED LIST

# Node class 

class Node: 

  

    # Function to initialise the node object 

    def __init__(self, data): 

        self.data = data # Assign data 

        self.next = None # Initialize next as null 

  

  

# Linked List class contains a Node object 

class LinkedList: 

  

    # Function to initialize head 

    def __init__(self): 

        self.head = None

  

def Circular(head):

    if head==None:

        return True

          

    # Next of head

    node = head.next

    i = 0

      

    # This loop would stop in both cases (1) If

    # Circular (2) Not circular

    while((node is not None) and (node is not head)):

        i = i + 1

        node = node.next

      

    return(node==head)

  

  

# Code execution starts here 

if __name__=='__main__':

    llist = LinkedList() 

    llist.head = Node(1)

    second = Node(2)

    third = Node(3) 

    fourth = Node(4)

      

    llist.head.next = second;

    second.next = third;

    third.next = fourth

      

    if (Circular(llist.head)):

        print('Yes')

    else:

        print('No')

      

    fourth.next = llist.head

      

    if (Circular(llist.head)):

        print('Yes')

    else:

        print('No')




OUTPUT

No
Yes

CREDITS: https://www.geeksforgeeks.org/check-if-a-linked-list-is-circular-linked-list/