Remove Duplicate Elements from a Doubly Linked List in Python

When it is required to remove the duplicate elements 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.

Below is a demonstration for the same −

Example

 Live Demo

class Node:
   def __init__(self, my_data):
      self.previous = None
      self.data = my_data
      self.next = None
class double_list:
   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 print_it(self):
      curr = self.head
      if (self.head == None):
         print("The list is empty")
         return
      print("The nodes in the doubly linked list are :")
      while curr != None:
         print(curr.data)
         curr = curr.next
   def remove_duplicates(self):
      if(self.head == None):
         return
      else:
         curr = self.head;
         while(curr != None):
            index_val = curr.next
            while(index_val != None):
               if(curr.data == index_val.data):
                  temp = index_val
                  index_val.previous.next = index_val.next
                  if(index_val.next != None):
                     index_val.next.previous = index_val.previous
                  temp = None
               index_val = index_val.next
            curr = curr.next
my_instance = double_list()
print("Elements are being added to the doubly linked list")
my_instance.add_data(10)
my_instance.add_data(24)
my_instance.add_data(54)
my_instance.add_data(77)
my_instance.add_data(24)
my_instance.print_it()
print("The elements in the list after removing duplicates are : ")
my_instance.remove_duplicates()
my_instance.print_it()

Output

Elements are being added to the doubly linked list
The nodes in the doubly linked list are :
10
24
54
77
24
The elements in the list after removing duplicates are :
The nodes in the doubly linked list are :
10
24
54
77

Explanation

• The ‘Node’ class is created.
• Another class with required attributes is created.
• Another method named ‘remove_duplicates’ is defined, that is used to remove the duplicate elements present in the linked list.
• Another method named ‘print_it’ is defined, that displays the nodes of the circular linked list.
• An object of the ‘double_list’ class is created, and the methods are called on it to add data.
• An ‘init’ method is defined, that the first and last nodes of the circular linked list to None.
• The ‘remove_duplicates’ method is called.
• It iterates through the list, and checks to see if any element has been repeated.
• If that is true, then it is deleted.
• This is displayed on the console using the ‘print_it’ method.