# 创建节点类
class Node():
def __init__(self,item):
# 节点数据
self.item=item
# 上一个节点地址
self.pre=None
# 下一个节点地址
self.next=None
class DoubleLinkList():
def __init__(self,node=None):
self.__head=node
#判断链表是否为空
def is_empty(self):
return self.__head is None
# 链表长度
def length(self):
cur=self.__head
count=0
while cur is not None:
cur=cur.next
count+=1
return count
# 循环链表
def travel(self):
cur=self.__head
while cur is not None:
print(cur.item,end='')
cur=cur.next
print('')
# 搜索节点
def search(self,item):
cur=self.__head
while cur is not None:
if cur.item==item:
return True
cur=cur.next
return False
# 头部增加节点
def add(self,item):
node=Node(item)
node.next=self.__head
self.__head=node
if node.next:
node.next.pre=node
# 尾部增加节点
def append(self,item):
node=Node(item)
if self.is_empty():
self.__head=node
else:
cur=self.__head
while cur.next is not None:
cur=cur.next
node.pre=cur
cur.next=node
# 指定位置插入
def insert(self,pos,item):
node=Node(item)
if pos<=0:
self.add(item)
elif pos>=self.length():
self.append(item)
else:
cur=self.__head
count=0
while count<pos-1:
cur=cur.next
count+=1
# 顺序赋值，先和上一个节点链接，再和下一个节点链接，然后下一个节点再和本节点链接
node.pre=cur.pre
cur.pre.next=node
node.next=cur
cur.pre=node
# 删除节点
def remove(self,item):
cur=self.__head
while cur is not None:
if cur.item==item:
if cur==self.__head:
self.__head=cur.next
if cur.next:
self.__head.pre=None
else:
cur.pre.next=cur.next
if cur.next:
cur.next.pre=cur.pre
return
cur=cur.next
if __name__ == '__main__':
dd=DoubleLinkList()
for i in range(10):
dd.append(i)
dd.travel()
print(dd.length())
dd.travel()
dd.add(1)
dd.travel()
dd.insert(4,5)
dd.travel()
dd.remove(5)
dd.travel()
dd.remove(5)
dd.travel()
