Remove Duplication in LinkedList

remove_dups_2_1.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Question.
# Write code to remove duplicates from an unsorted linked list.
# Follow UP
# How would you solve this problem if a temporary buffer is not allowed?

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

  def __str__(self):
    return "%d" % (self.value)

class LinkedList:
  def __init__(self):
    self.edge_node = None

  def add_node(self, node):
    self.edge_node = node

  def add(self, node_value):
    new_node = Node(node_value, self.edge_node)
    self.add_node(new_node)

    return new_node

  def remove_duplicates(self):
    exists_vaues = [] # to Hash
    pre_node = None
    cur_node = self.edge_node
    while cur_node:
      if cur_node.value in exists_vaues:
        pre_node.next_ptr = cur_node.next_ptr
      else:
        exists_vaues.append(cur_node.value)
        pre_node = cur_node

      cur_node = cur_node.next_ptr

  def __str__(self):
    node_value_arr = []
    node = self.edge_node
    while node:
      node_value_arr.append(str(node))
      node = node.next_ptr

    return " -> ".join(node_value_arr)

if __name__ == '__main__':
  # Setup linkedlist
  linked_list = LinkedList()

  node_5 = linked_list.add(5)
  node_3_2 = linked_list.add(3) # Make duplicate
  node_4_3 = linked_list.add(4)
  node_4_2 = linked_list.add(4)
  node_4 = linked_list.add(4)
  node_3 = linked_list.add(3)
  node_2_2 = linked_list.add(2) # Make duplicate
  node_2 = linked_list.add(2)
  node_1_2 = linked_list.add(1) # Make duplicate
  node_1 = linked_list.add(1)


  print "Before removing duplicates"
  print linked_list

  linked_list.remove_duplicates()

  print "After removing duplicates"
  print linked_list