双向链表

class Node():

def __init__(self,item,pre=None,next=None):

self.item = item

self.next = next

self.pre = pre

class DoubleLinkList():

def __init__(self,node=None):

self.__head = node

def search(self,item):

cur = self.__head

while cur != None:

if cur.item == item:

return True

cur = cur.next

return False

def length(self):

cur = self.__head

count = 0

while cur != None:

count += 1

cur = cur.next

return count

def add(self,item):

node = Node(item)

if self.is_empty():

# 如果是空链表，将__head指向node

self.__head = node

else:

# 将node的next指向__head的头节点

node.next = self.__head

# 将__head的头节点的prev指向node

self.__head.pre = node

# 将__head 指向node

self.__head = node

def append(self, item):

node = Node(item)

if self.is_empty():

# 如果是空链表，将_head指向node

self.__head = node

else:

# 移动到链表尾部

cur = self.__head

while cur.next != None:

cur = cur.next

# 将尾节点cur的next指向node

cur.next = node

# 将node的prev指向cur

node.pre = cur

def travel(self):

cur = self.__head

while cur != None:

print (cur.item)

cur = cur.next

 

def is_empty(self):

return self.__head == None

def remove(self, item):

if self.is_empty():

return

else:

cur = self.__head

if cur.item == item:

# 如果首节点的元素即是要删除的元素

if cur.next == None:

# 如果链表只有这一个节点

self.__head = None

else:

# 将第二个节点的prev设置为None

cur.next.prev = None

# 将__head指向第二个节点

self.__head = cur.next

return

while cur != None:

if cur.item == item:

# 将cur的前一个节点的next指向cur的后一个节点

cur.pre.next = cur.next

# 将cur的后一个节点的prev指向cur的前一个节点

cur.next.pre = cur.pre

break

cur = cur.next

def insert(self, pos, item):

if pos <= 0:

self.add(item)

elif pos > (self.length()-1):

self.append(item)

else:

node = Node(item)

cur = self.__head

count = 0

# 移动到指定位置的前一个位置

while count < (pos-1):

count += 1

cur = cur.next

# 将node的prev指向cur

node.pre = cur

# 将node的next指向cur的下一个节点

node.next = cur.next

# 将cur的下一个节点的prev指向node

cur.next.pre = node

# 将cur的next指向node

cur.next = node

#导入单链表模块的类from singe_next import SingleLinkList#

if __name__ == "__main__":

ll = DoubleLinkList()

ll.add(1)

ll.add(0)

ll.append(0)

ll.insert(2, 4)

ll.insert(3, 4)

ll.insert(1, 5)

print ("length:", ll.length())

ll.travel()

print (ll.search(2))

print (ll.search(3))

ll.remove(1)

print ("length:", ll.length())

ll.travel()