class Node(object): # 结点有两个指针
def __init__(self, maxsize = None, value = None, next = None, prev = None):
self.maxsize = maxsize
self.value = value
self.next = next
self.prev = prev
class Stack(object):
def __init__(self, maxsize = None):
self.maxsize = maxsize
node = Node()
node.next = node
node.prev = node # 最开始的只有根结点，它自己两个指针指向自己
self.root = node
self.length = 0
def __len__(self):
return self.length
def headnode(self):
return self.root.next
def tailnode(self):
return self.root.prev
def push(self, value): # 在右端压入值，相当于循环双端链表的append
if self.maxsize is not None and len(self) >= self.maxsize:
raise Exception('full')
node = Node(value = value)
tailnode = self.tailnode() # 获取尾结点， 这个这次append 是插入的第一个结点。 尾结点就是self.root (根结点)
tailnode.next = node
node.prev = tailnode
node.next = self.root
self.root.prev = node
self.length += 1
def remove(self, node): # 注意这里传入的是一个node， 不是传入一个值。 为了，降低算法复杂度
if node is self.root:
return "不能移除根结点"
node.prev.next = node.next
node.next.prev = node.prev
self.length -= 1
del node
def iter_node(self): # 遍历结点
if self.root.next == self.root: # 只有根结点
return "队列为空"
curnode = self.root.next
while curnode.next is not self.root:
yield curnode
curnode = curnode.next
yield curnode # 尾结点也要遍历
def __iter__(self):
for node in self.iter_node():
yield node.value
def iter_node_reverse(self): # 反向遍历
if self.root.prev is self.root:
return
curnode = self.root.prev # tailnode
while curnode.prev is not self.root:
yield curnode
curnode = curnode.prev
yield curnode
def pop(self):
if len(self) ==0:
raise Exception('empty')
tailnode = self.tailnode()
value = tailnode.value
self.remove(tailnode)
return value
def test_stack():
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
assert len(stack) == 3
a = stack.pop()
assert len(stack) == 2
assert a == 3
