# -*- coding:utf-8 -*-
#! python3
class Node():
  def __init__(self,item):
    #初始化这个节点，值和下一个指向
    self.item = item
    self.next = None
class SingleLinklist():
  def __init__(self):
    #初始化这个单链表的头指针为空
    self._head = None
  def length(self):
    #获取这个链表的长度
    count = 0
    cur = self._head
    while cur != None:
      count+=1
      cur = cur.next
    return count
  def is_empty(self):
    """判断是否为空"""
    return self._head == None
  def add(self,item):
    """在头部添加元素"""
    node = Node(item)
    node.next = self._head
    self._head = node
  def append(self,item):
    """在尾部添加元素"""
    cur = self._head
    node = Node(item)
    while cur != None:
      cur = cur.next
    cur.next = node
  def insert(self,pos,item):
    """在选定的位置添加元素"""
    cur = self._head
    node = Node(item)
    count = 0
    if pos <= 0:
      self.add(item)
    elif pos > (self.length()-1):
      self.append(item)
    else:
      while count < (pos -1):
        count+=1
        cur = cur.next
      node.next = cur.next
      cur.next = node
  def travel(self):
    """遍历整个链表"""
    cur = self._head
    while cur != None:
      print(cur.item,end=" ")
      cur = cur.next
    print(" ")
  def remove(self,item):
    """删除链表"""
    cur = self._head
    pre =None
    while cur != None:
      if cur.item == item:
        if not pre:
          self._head = cur.next
          break
        else:
          pre.next = cur.next
      else:
        pre = cur #
        cur = cur.next
  def search(self,item):
    """查找某个节点"""
    cur = self._head
    while cur != None:
      if cur.item == item:
        print("找到这个元素了")
        return True
      cur = cur.next
    print("抱歉没有这个元素")
    return False
singlistdemo = SingleLinklist()
singlistdemo.add(1)
singlistdemo.add(2)
singlistdemo.add(65)
singlistdemo.insert(2,77)
singlistdemo.insert(1,66)
singlistdemo.insert(0,66)
print(singlistdemo.length())
singlistdemo.travel()
singlistdemo.remove(1)
singlistdemo.travel()
singlistdemo.search(65)