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

class LinkedList_structure:
   def __init__(self):
      self.head = None
      self.last_node = None

   def add_vals(self, data):
      if self.last_node is None:
         self.head = Node(data)
         self.last_node = self.head
      else:
         self.last_node.next = Node(data)
         self.last_node = self.last_node.next

def list_length(my_list):
   my_len = 0
   curr = my_list.head
   while curr:
      curr = curr.next
      my_len = my_len + 1
   return my_len

def return_from_end(my_list, n):
   l = list_length(my_list)
   curr = my_list.head
   for i in range(l - n):
      curr = curr.next
   return curr.data

my_instance = LinkedList_structure()

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

n = int(input('Enter the value for n.. '))
my_result = return_from_end(my_instance, n)

print('倒数第N个元素是: {}'.format(my_result))

Enter the elements of the linked list..45 31 20 87 4
Enter the value for n.. 2
倒数第N个元素是: 87