Python program to rotate doubly linked list by N nodes

When it is required to rotate a doubly linked list by a specific number of nodes, 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
      self.size = 0
   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
         self.size = self.size + 1;
   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 rotate_list(self, num):
      curr = self.head;
      if(num == 0 or num >= self.size):
         return;
      else:
         for i in range(1, num):
            curr = curr.next;
         self.tail.next = self.head;
         self.head = curr.next;
         self.head.previous = None;
         self.tail = curr;
         self.tail.next = None;
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.add_data(0)
my_instance.print_it()
print("The elements in the list after rotating : ")
my_instance.rotate_list(4)
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
0
The elements in the list after rotating :
The nodes in the doubly linked list are :
24
0
10
24
54
77

Explanation

• The ‘Node’ class is created.
• Another class with required attributes is created.
• Another method named ‘add_data’ is defined, that is used to add data to the circular linked list.
• Another method named ‘rotate_list’ is defined, that uses the specific node as pivot and rotates the list, thereby moving the elements to a different position.
• Another method named ‘print_it’ is defined that is used to display the linked list data on the console.
• An object of the ‘double_list’ class is created, and the methods are called on it to add data.
• The ‘rotate_list’ method is called.
• It iterates through the nodes in the linked list, gets the middle most index and starts deleting the elements.
• This is displayed on the console using the ‘print_it’ method.