class Node(object):
"""结点"""
def __init__(self, data):
self.data = data
self.pre = None
self.next = None
class DoubleLinkList(object):
"""双链表"""
def __init__(self, node=None):
self.__head = node
def is_empty(self):
"""判断链表是否为空"""
return self.__head is None
def length(self):
"""链表的长度"""
count = 0
cur = self.__head
while cur is not None:
count += 1
cur = cur.next
return count
def travel(self):
"""遍历整个链表"""
cur = self.__head
while cur is not None:
print(cur.data, end="")
cur = cur.next
print()
def add(self, item):
"""头插"""
node = Node(item)
# 空链表头插
if self.is_empty():
self.__head = node
# 非空链表头插
else:
node.next = self.__head
self.__head.pre = node
self.__head = node
def append(self, item):
"""尾插"""
node = Node(item)
# 空链表尾插
if self.is_empty():
self.__head = node
# 非空链表尾插
else:
cur = self.__head
# 找到最后一个结点
while cur.next is not None:
cur = cur.next
cur.next = node
node.pre = cur
def insert(self, pos, item):
"""指定位置插入"""
if pos <= 0:
self.add(item)
elif pos > self.length() - 1:
self.append(item)
else:
node = Node(item)
cur = self.__head
count = 0
# 找到指定位置的前一个结点
while count < pos - 1:
cur = cur.next
count += 1
node.next = cur.next
node.pre = cur
cur.next = node
node.next.pre = node
def remove(self, item):
"""删除指定结点"""
cur = self.__head
while cur is not None:
# 找到要删除的结点
if cur.data == item:
# 如果要删除的结点是头结点
if cur == self.__head:
self.__head = cur.next
# 判断链表是否只有一个结点
if cur.next:
cur.next.pre = None
# 要删除的结点不是头结点
else:
cur.pre.next = cur.next
# 判断要删除的结点是否是尾结点
if cur.next:
cur.next.pre = cur.pre
return
else:
cur = cur.next
def search(self, item):
"""查找结点是否存在"""
cur = self.__head
while cur is not None:
if cur.data == item:
return True
else:
cur = cur.next
return False
if __name__ == '__main__':
sll = DoubleLinkList()
print(sll.is_empty())
print(sll.length())
sll.add(1)
sll.remove(1)
print(sll.is_empty())
print(sll.length())
sll.append(2)
sll.append(3)
sll.append(4)
sll.append(5)
sll.travel() # 2345
print(sll.length()) # 4
sll.add(99) # 99 2345
sll.travel()
print(sll.length()) # 5
print(sll.search(6)) # False
print(sll.search(4)) # True
sll.remove(5)
sll.travel() # 99 234