class Node(object):
def __init__(self, elem):
"""
:param elem: 表元素域
next：下一结点链接域
cursor(cur)：游标
"""
self.elem = elem
# 定义next指向空
self.next = None
# 定义next指向空
self.prev = None
class DoubleLinkList(object):
"""
一种更复杂的链表是“双向链表"或“双面链表"。每个节点有两个链接: 一个指向前一个节点，当此节点为第
一个节点时，指向空值;而另一个指向下一个节点，当此节点为最后一个节点时，指向空值。
"""
def __init__(self, node=None):
self._head = node # node.elem node.next
def is_empty(self):
"""链表是否为空 """
return self._head is None
def length(self):
"""链表长度"""
# cur游标，用来移动遍历节点
cur = self._head
count = 0
while cur is not None:
count += 1
cur = cur.next
# count 记录数量
return count
def travel(self):
"""遍历整个链表"""
cur = self._head
while cur is not None:
print(cur.elem, end=' ')
cur = cur.next
def add(self, item):
"""链表头部添加元素：头插法"""
node = Node(item)
# node的next指向_head
node.next = self._head
# _head指向新节点
self._head = node
node.next.prev = node
def append(self, item):
"""链表尾部添加元素:尾插法"""
node = Node(item)
# 下一结点链接域不为空
if self.is_empty():
self._head = node
else:
cur = self._head
while cur.next is not None:
cur = cur.next
cur.next = node
node.prev = cur
def insert(self, pos, item):
"""
pos: pos从0开始
pre:指定节点前一节点，相当于游标
node：插入的指定节点
指定位置添加元素
"""
# if pos<=0 头插法
if pos <= 0:
self.add(item)
# elif pos>(self.length()-1) 尾插法
elif pos > (self.length() - 1):
self.append(item)
# else 插入法
else:
cur = self._head
count = 0
# 当循环退出后，cur指向pos
while count < pos:
count += 1
cur = cur.next
# 当循环退出后，cur指向pos位置
node = Node(item)
# 方式1：
node.next = cur
node.prev = cur.prev
cur.prev.next = node
cur.prev = node
# 方式2：
# node.next = cur
# node.prev = cur.prev
# cur.prev = node
# node.prev.next = node
def remove(self, item):
"""删除元素"""
# 考虑删除头部、尾部、中间节点
cur = self._head
while cur is not None:
if cur.elem == item:
# 先判断是否是头节点
if cur == self._head:
self._head = cur.next
if cur.next: # 判断链表表是否只有一个节点
cur.next.prev = None
else:
cur.prev.next = cur.next
if cur.next: # 判断链表是否是最后一个节点
cur.next.prev = cur.prev
break
else:
cur = cur.next
def search(self, item):
"""查找节点是否存在"""
# 1. 创建游标
cur = self._head
# 2. 遍历游标
while cur is not None:
# 3. cur.elem = item
if cur.elem == item:
return True
else:
cur = cur.next
return False
if __name__ == '__main__':
DLL = DoubleLinkList()
DLL.is_empty()
l1 = DLL.length()
print(l1)
DLL.append(55)
DLL.is_empty()
l2 = DLL.length()
print(l2)
DLL.append(2)
DLL.add(8)
DLL.append(3)
DLL.append(4)
DLL.append(5)
# 55 1 8 2 3 4
DLL.insert(-1, 9) # 9 8 55 2 1 8 2345
DLL.insert(2, 100) # 9 8 100 55 2 1 8 2345
DLL.travel()
