也是搬砖和练习, 这段代码应该是 2年前了, 也是从网上找的, 然后记录学习, 当时也没太理解, 慢慢随着时间的流逝, 也有了一些积淀, 这样再回头来看一两前的东西, 就比较好理解了. 最近又在疯狂加班, 搞BI, 数据处理最难的部分, 写了2000多sql.. 然后还不算上前端的 sql..写了整整半个月, 都麻木了, 奇怪的一点是, 每次我想放弃的时候, 灵感就来了, 真的是又爱又恨, 工作占据了 95% 的时间, 就自己额外学的时间急剧压缩, 毕竟一个人第一次真正意义上搞了个大项目, 前后端, 数据库, 所有逻辑的实现... 也是快速成长吧, 对自己.
不扯了, 回归主题, 来复习一把双链表即一个节点,有前驱和后继, .. 不想解释啥, 直接贴代码会更加直观.
实现(参照单链表)
class Node:
"""节点类"""
def __init__(self, data=None):
self.data = data
self.next = None
self.prior = None
class DoubleLinkList:
"""双向链表"""
def __init__(self, node=None):
"""双向链表头节点"""
self.__head = node
@property
def is_empty(self):
"""链表是否为空"""
return self.__head is None
@property
def length(self):
"""链表长度(元素个数)"""
current = self.__head
count = 0
while current is not None:
count += 1
current = current.next # 游标不断往后移动
return count
def travel(self):
"""遍历链表"""
current = self.__head
while current is not None:
print(current.data)
current = current.next
def add(self, item):
"""头部插入元素"""
node = Node(item)
# 方案: 以node先启动 (一定要有画面感,或者直接画出来)
# 顺序a: 1. node.next -> self.__head; 2. self.__head -> node; 3. node.next.prior -> node
# 顺序b: 1. node.next -> self.__head; 2. self.__head.prior=node; 3.self.__head=node
if self.is_empty:
self.__head = node
else:
node.next = self.__head # 让node的nxet-> 原来self.__head的指向元素
self.__head = node
node.next.prior = node
def append(self, item):
"""尾部插入元素"""
node = Node(item)
if self.is_empty:
self.__head = node
else:
current = self.__head
while current.next:
current = current.next
# 此时游标已移动到最后一个节点
current.next = node
node.prior = current
def insert(self, position, item):
"""从指定位置下标去插入元素"""
if position <= 0:
self.add(item)
elif position > self.length - 1:
self.append(item)
else:
current = self.__head
count = 0
while count < position:
count += 1
current = current.next
# 游标定位到postion处,顺序断链即可, 注意顺序能够找到前后元素哈
node = Node(item)
node.next = current
node.prior = current.prior
# 前后继联系
#current.prior.next = node; current.prior = node, 代码不唯一,关键在于如何去打断节点和连接
current.prior = node
node.prior.next = node
def search(self, item):
"""搜索元素并范围其位置-首次被找到"""
current = self.__head
while current:
if current.data == item:
return True
current = current.next
return False
def remove(self, item):
"""删除元素, 首次被找到"""
current = self.__head
while current:
if current.data == item:
# 判断是否为头结点, 如果是头节点,则 self.__head -> current.next
if current == self.__head:
self.__head = current.next
# 判断链表是否只有一个节点
if current.next:
current.next.prior = None
else:
# A, B, C 删除B: B.prior.next -> B.next; B.next.prior -> B.prior
current.prior.next = current.next
if current.next:
current.next.prior = current.prior
break
else:
# 移动指针
current = current.next
l = DoubleLinkList()
l.append(2)
l.add(1)
l.append(4)
l.travel()
1
2
4
# l.add('99')
l.insert(3,'一波带走')
l.travel()
1
2
4
一波带走
l.remove(4)
l.travel()
1
2
哈哈哈