# -*- coding: utf-8 -*-
class Node(object):
def __init__(self, value=None, prev=None, next=None):
self.value, self.prev, self.next = value, prev, next
class CircularDoubleLinkedList(object):
"""循环双端链表 ADT
多了个循环其实就是把 root 的 prev 指向 tail 节点,串起来
"""
def __init__(self, maxsize=None):
self.maxsize = maxsize
node = Node()
node.next, node.prev = node, node
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 append(self, value): # O(1), 你发现一般不用 for 循环的就是 O(1),有限个步骤
if self.maxsize is not None and len(self) > self.maxsize:
raise Exception('LinkedList is Full')
node = Node(value=value)
tailnode = self.tailnode() or self.root # or self.root 没有看明白
tailnode.next = node
node.prev = tailnode
node.next = self.root
self.root.prev = node
self.length += 1
def appendleft(self, value):
if self.maxsize is not None and len(self) > self.maxsize:
raise Exception('LinkedList is Full')
node = Node(value=value)
if self.root.next is self.root: # empty
node.next = self.root
node.prev = self.root
self.root.next = node
self.root.prev = node
else:
node.prev = self.root
headnode = self.root.next
node.next = headnode
headnode.prev = node
self.root.next = node
self.length += 1
def remove(self, node): # O(1),传入node 而不是 value 我们就能实现 O(1) 删除
"""remove
:param node # 在 lru_cache 里实际上根据key 保存了整个node:
"""
if node is self.root:
return
else: #
node.prev.next = node.next
node.next.prev = node.prev
self.length -= 1
return node
def iter_node(self):
if self.root.next is self.root:
return
curnode = self.root.next
while curnode.next is not self.root:
yield curnode
curnode = curnode.next
yield curnode
def __iter__(self):
for node in self.iter_node():
yield node.value
def iter_node_reverse(self):
"""相比单链表独有的反序遍历"""
if self.root.prev is self.root:
return
curnode = self.root.prev
while curnode.prev is not self.root:
yield curnode
curnode = curnode.prev
yield curnode
def test_double_link_list():
dll = CircularDoubleLinkedList()
assert len(dll) == 0
dll.append(0)
dll.append(1)
dll.append(2)
assert list(dll) == [0, 1, 2]
assert [node.value for node in dll.iter_node()] == [0, 1, 2]
assert [node.value for node in dll.iter_node_reverse()] == [2, 1, 0]
headnode = dll.headnode()
assert headnode.value == 0
dll.remove(headnode)
assert len(dll) == 2
assert [node.value for node in dll.iter_node()] == [1, 2]
dll.appendleft(0)
assert [node.value for node in dll.iter_node()] == [0, 1, 2]
if __name__ == '__main__':
test_double_link_list()
Python数据结构 双链表
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转载自blog.csdn.net/weixin_37392582/article/details/80576781
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