#coding:utf-8
class Node(object):
  def __init__(self, data):
    self.data = data
    self.next = None
class NodeList(object):
  def __init__(self, node):
    self.head = node
    self.head.next = None
    self.end = self.head
  def add_node(self, node):
    self.end.next = node
    self.end = self.end.next
  def length(self):
    node = self.head
    count = 1
    while node.next is not None:
      count += 1
      node = node.next
    return count
  # delete node and return it's value
  def delete_node(self, index):
    if index+1 > self.length():
      raise IndexError('index out of bounds')
    i = 0
    node = self.head
    while True:
      if i==index-1:
        break
      node = node.next
      i += 1
    tmp_node = node.next
    node.next = node.next.next
    return tmp_node.data
  def show(self):
    node = self.head
    node_str = ''
    while node is not None:
      if node.next is not None:
        node_str += str(node.data) + '->'
      else:
        node_str += str(node.data)
      node = node.next
    print node_str
  # Modify the original position value and return the old value
  def change(self, index, data):
    if index+1 > self.length():
      raise IndexError('index out of bounds')
    i = 0
    node = self.head
    while True:
      if i == index:
        break
      node = node.next
      i += 1
    tmp_data = node.data
    node.data = data
    return tmp_data
  # To find the location of index value
  def find(self, index):
    if index+1 > self.length():
      raise IndexError('index out of bounds')
    i = 0
    node = self.head
    while True:
      if i == index:
        break
      node = node.next
      i += 1
    return node.data
#test case
n1 = Node(0)
n2 = Node(1)
n3 = Node(2)
n4 = Node(3)
n5 = Node(4)
node_list = NodeList(n1)
node_list.add_node(n2)
node_list.add_node(n3)
node_list.add_node(n4)
node_list.add_node(n5)
#node = node_list.delete_node(3)
#print node
#d = node_list.change(0,88)
data = node_list.find(5)
print data
node_list.show()