#!/usr/bin/env python

 # -*- coding:utf-8 -*-

 from chapter3.single_linked_list import LNode,LinkedListUnderflow,LList

 import random

 class LList1(LList):

     def __init__(self):

         LList.__init__(self)

         self._rear = None

     #表头插入

     def prepend(self, elem):

         if self._head is None:

             self._head = LNode(elem)

             self._rear = self._head

         else:

             self._head = LNode(elem, self._head)

     #表尾插入

     def append(self, elem):

         if self._head is None:

             self._head = LNode(elem)

             self._rear = self._head

         else:

             self._rear.next = LNode(elem)

             self._rear = self._rear.next

     #表头删除

     def pop(self):

         if self._head is None:

             raise LinkedListUnderflow("in pop")

         e = self._head.elem

         self._head = self._head.next

         return e

         #self._rear不变仍然指向最后一个元素

     #表尾删除

     def pop_last(self):

         p = self._head

         if p is None:

             raise LinkedListUnderflow("in pop_last")

         if p.next is None:

             self._head = None

         while p.next.next:

             p = p.next

         e = p.next.elem

         p.next = None

         self._rear = p

         return e

 if __name__=="__main__":

     mlist1 = LList1()

     mlist1.prepend(98)

     mlist1.printall()

     for i in range(10,20):

         mlist1.append(random.randint(1,20))

     mlist1.printall()

     for i in mlist1.filter(lambda y: y%2 == 0):

         print(i)