Find Largest Element in a Doubly Linked List using Python

When it is required to find the largest element in a doubly linked list, a method to add elements to the doubly linked list, a method to print the elements of the doubly linked list, and a method to find the largest element in a doubly linked list are defined.

Below is a demonstration for the same −

Example

 Live Demo

class Node:
   def __init__(self, data):
      self.data = data
      self.next = None
      self.prev = None

class DoublyLinkedList_structure:
   def __init__(self):
      self.first = None
      self.last = None

   def add_vals(self, data):
      self.insert_at_end(Node(data))

   def insert_at_end(self, newNode):
      if self.last is None:
         self.last = newNode
         self.first = newNode
      else:
         newNode.prev = self.last
         self.last.next = newNode
         self.last = newNode

def find_largest_val(my_list):
   if my_list.first is None:
      return None
   largest_val = my_list.first.data
   curr = my_list.first.next
   while curr:
      if curr.data > largest_val:
         largest_val = curr.data
      curr = curr.next
   return largest_val

my_instance = DoublyLinkedList_structure()

my_list = input('Enter the elements in the doubly linked list ').split()
for elem in my_list:
   my_instance.add_vals(int(elem))

largest_val = find_largest_val(my_instance)
if largest_val:
   print('The largest element is {}.'.format(largest_val))
else:
   print('The list is empty.')

Output

Enter the elements in the doubly linked list 45 12 67 89 234 567 888 44 999
The largest element is 999.

Explanation

• The ‘Node’ class is created.

• Another ‘DoublyLinkedList_structure’ class with required attributes is created.

• It has an ‘init’ function that is used to initialize the first element, i.e the ‘head’ to ‘None’.

• A method named ‘add_vals’ is defined, that helps add a value to the stack.

• Another method named ‘insert_at_end’ is defined, that helps add a value to the end of the doubly linked list.

• Another method named ‘find_largest_val’ is defined, that helps find the largest value in the entire doubly linked list.

• An instance of the ‘DoublyLinkedList_structure’ is created.

• Elements are added to the linked list.

• The ‘find_largest_val’ method is called on this doubly linked list.

• The output is displayed on the console.