Python program to create a Circular Linked List of N nodes and count the number of nodes

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Python program to create a Circular Linked List of N nodes and count the number of nodes

In this program, we have to find out the number of nodes present in the circular linked list. We first create the circular linked list, then traverse through the list and increment variable ‘count’ by 1.

ALGORITHM:

  1. Define a Node class which represents a node in the list. It has two properties data and next which will point to the next node.
  2. Define another class for creating the circular linked list, and it has two nodes: head and tail. It has two methods: add() and display() .
  3. add() will add the node to the list:
  • It first checks whether size is null or head is null; then it will insert the node as the head.
  • Both head and tail will point to a newly added node.
  • If the head is not null, the new node will be the new tail, and the new tail will point to the head as it is a circular linked list.

a. countNodes() will count the number of nodes present in the list.

  • Define new node current which will point to the head node.
  • Traverse through the list to count the nodes by making the current node to point to next node in the list till current points to head again.

PROGRAM:

  1. #Represents the node of the list.  
  2. class Node:
  3.     def __init__(self,data):
  4.         self.data = data;
  5.         self.next = None;
  6. class CreateList:
  7.     #Declaring head and tail pointer as null.  
  8.     def __init__(self):
  9.         self.count = 0;
  10.         self.head = Node(None);
  11.         self.tail = Node(None);
  12.         self.head.next = self.tail;
  13.         self.tail.next = self.head;
  14.     #This function will add the new node at the end of the list.  
  15.     def add(self,data):
  16.         newNode = Node(data);
  17.         #Checks if the list is empty.  
  18.         if self.head.data is None:
  19.             #If list is empty, both head and tail would point to new node.  
  20.             self.head = newNode;
  21.             self.tail = newNode;
  22.             newNode.next = self.head;
  23.         else:
  24.             #tail will point to new node.  
  25.             self.tail.next = newNode;
  26.             #New node will become new tail.  
  27.             self.tail = newNode;
  28.             #Since, it is circular linked list tail will point to head.  
  29.             self.tail.next = self.head;
  30.     #This function will count the nodes of circular linked list  
  31.     def countNodes(self):
  32.         current = self.head;
  33.         self.count=self.count+1;
  34.         while(current.next != self.head):
  35.             self.count=self.count+1;
  36.             current = current.next;
  37.         print(“Count of nodes present in circular linked list: “),
  38.         print(self.count);
  39. class CircularLinkedList:
  40.     cl = CreateList();
  41.     #Adds data to the list  
  42.     cl.add(1);
  43.     cl.add(2);
  44.     cl.add(4);
  45.     cl.add(1);
  46.     cl.add(2);
  47.     cl.add(3);
  48.     #Displays all the nodes present in the list  
  49.     cl.countNodes();

Output:

Count of nodes present in circular linked list:
6

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