When it is required to count the number of nodes in a doubly linked list, a ‘Node’ class needs to be created. In this class, there are three attributes, the data that is present in the node, the access to the next node of the linked list, and the access to the previous node of the linked list.
In a doubly linked list, the nodes have pointers. The current node would have a pointer to the next node as well as the previous node. The last value in the list will have ‘NULL’ value in the next pointer. It can be traversed in both the directions.
Below is a demonstration for the same −
class Node: def __init__(self, my_data): self.prev = None self.data = my_data self.next = None class count_val: def __init__(self): self.head = None self.tail = None def add_data(self, my_data): new_node = Node(my_data) if(self.head == None): self.head = self.tail = new_node; self.head.previous = None; self.tail.next = None; else: self.tail.next = new_node; new_node.previous = self.tail; self.tail = new_node; self.tail.next = None; def count_node(self): my_counter = 0; curr = self.head; while(curr != None): my_counter = my_counter + 1; curr = curr.next; return my_counter; def print_it(self): curr = self.head if (self.head == None): print("The list is empty") return print("The nodes are :") while curr != None: print(curr.data) curr = curr.next my_instance = count_val() print("Elements are being added to the list") my_instance.add_data(10) my_instance.add_data(14) my_instance.add_data(24) my_instance.add_data(17) my_instance.add_data(22) my_instance.print_it() print("The nodes in the doubly linked list are : ") print(my_instance.count_node())
Elements are being added to the list The nodes are : 10 14 24 17 22 The nodes in the doubly linked list are : 5