python实现双向链表

class Node(object):
def __init__(self, value):
self.value = value
self.next = None
self.prev = None

class LinkList(object):
def __init__(self):
self.head = Node('head')

def add(self, value):
p = self.head
new = Node(value)
while p.next:
p = p.next
p.next = new
new.prev = p

def remove(self, value):
p = self.head
while p.next:
if p.value == value:
temp = p.prev
xyz = p.next
temp.next = xyz
xyz.prev = temp
break
else:
p = p.next

def find(self, value):
#根据指定的值找出位置
p = self.head
i = 0
while p.next:
if p.value == value:
return i
else:
p = p.next
i += 1

raise AttributeError(u"can\'t find this element")

def index(self, index):
#根据指定的位置找出相应的值
i = 0
p = self.head
while p.next:
if i == index:
return p.value
else:
i += 1
p = p.next
raise IndexError(u'index out of range')

def findprev(self, value):
"""根据指定节点的值找出前面的一个节点的值"""
p = self.head
while 1:
if p.value == value:
return p.prev.value
break
else:
p = p.next
if not p.next:
return p.prev.value
break

raise AttributeError(u"can\'t find this element")

def findnext(self, value):
"""根据指定节点的值找出后面的一个节点的值"""
p = self.head
while 1:
if p.value == value:
return p.next.value
else:
p = p.next
if not p.next:
return None
raise AttributeError(u"can\'t find this element")

def insert(self, index, value):
"""index必须大于等于1
"""
i = 0
p = self.head
new = Node(value)
while p.next:
if i == index:
temp = p.prev
temp.next = new
new.prev = temp
new.next = p
p.prev = new
break
else:
p = p.next
i += 1
#上面循环自然结束,就直接插入到元素的末尾
else:
p.next = new
new.prev = p

def length(self):
p = self.head
i = 0
while p.next:
p = p.next
i += 1

return i

def output(self):
p = self.head
while 1:
print p.value
p = p.next
if not p.next:
print p.value
break

def reverse(self):
"""反转链表"""
length = self.length()
i = 0
p = self.head.next
while p.next:
p = p.next
else:
last = p
first = self.head.next
while i < length:
first.value, last.value = last.value, first.value
first = first.next
last = last.prev
i += 1
length -= 1