Features:
len: O(1), get the length of the linked list
head: O(1), the first node at the head
tail: O(1) the first node at the tail
No loop: non Circular linked list
#void *: Store any type of data. (Dynamic language comes naturally)
Create/destroy/initialize:
##Source code
Python dynamic language needs to manually manage memory application and release.
Use generators to lazily implement forward and reverse traversal.
"""
参考redis adlist.c. 实现双链表相关的api
head tail
None <- <- <-
1 2 3
-> -> -> None
len:3
"""
import copy
from typing import Any
class Node(object):
def __init__(self, data) -> None:
self.next = None
self.pre = None
self.data = data
def __str__(self) -> str:
return f"{self.data}"
class DLinkList(object):
def __init__(self) -> None:
self.head = None
self.tail = None
self.len = 0
def empty(self) -> None:
self.head = None
self.tail = None
self.len = 0
def add_node_head(self, data=None) -> Node:
"""[头插法]
Args:
data ([type], optional): [description]. Defaults to None.
"""
new_node = Node(data=data)
if self.len == 0:
# 链表为空. 处理头/尾指针
self.tail = new_node
self.head = new_node
else:
# 插入新节点
new_node.next = self.head
self.head.pre = new_node
self.head = new_node
self.len += 1
return new_node
def add_node_tail(self, data: Any=None) -> Node:
"""[尾插法]
Args:
data ([type], optional): [description]. Defaults to None.
"""
new_node = Node(data=data)
if self.len == 0:
# 链表为空. 处理头/尾指针
self.tail = new_node
self.head = new_node
else:
# 插入新节点
new_node.pre = self.tail
new_node.next = self.tail.next
self.tail.next = new_node
# 更新尾指针
self.tail = new_node
self.len += 1
return new_node
def insert_node(self, old_node: Node=None, data: Any=None, after: bool=False) -> None:
"""[插入新节点, 在旧节点的前/后]
Args:
old_node (Node, optional): [旧节点]. Defaults to None.
data (Any, optional): [新数据]. Defaults to None.
after (Bool, optional): [是否在之后插入]. Defaults to False.
"""
assert self.len, f"self.len({self.len}) must > 0"
new_node = Node(data=data)
if after:
new_node.pre = old_node
new_node.next = old_node.next
old_node.next.pre = new_node
old_node.next = new_node
if self.tail == old_node:
self.tail = new_node
else:
new_node.pre = old_node.pre
new_node.next = old_node
old_node.pre.next = new_node
old_node.pre = new_node
if self.head == old_node:
self.head = new_node
self.len += 1
def del_node(self, node: Node) -> None:
"""[删除节点]
Args:
node (Node): [description]
"""
assert self.len, "DLinklist is None"
if not node:
return
if node == self.head:
self.head = node.next
else:
# 1.处理next
node.pre.next = node.next
if node == self.tail:
self.tail = node.pre
else:
# 2.处理pre
node.next.pre = node.pre
node.pre = None
node.next = None
del node
self.len -= 1
def next(self, reversed:bool=False):
"""[获取生成器]
Args:
reversed (bool, optional): [description]. Defaults to False.
Returns:
[type]: [description]
"""
if reversed:
return self._reverse_next()
return self._next()
def _reverse_next(self):
"""[反向迭代, 使用生成器记录状态]
Yields:
[type]: [description]
"""
cur = self.tail
idx = self.len - 1
while cur:
yield (idx, cur)
idx -= 1
cur = cur.pre
def _next(self):
"""[正向迭代, 使用生成器记录状态]]
Yields:
[type]: [description]
"""
cur = self.head
idx = 0
while cur:
yield (idx, cur)
idx += 1
cur = cur.next
def dup(self):
return copy.deepcopy(self)
def find(self, key: Any=None) -> tuple:
if not key:
return
g = self.next()
for idx, node in g:
if node.data == key:
return idx, node
return -1, None
def rotate_tail_to_head(self) -> None:
"""[正向旋转节点]
移动尾节点，插入到头部
"""
assert self.len >= 2, "dlist len must >=2"
head = self.head
tail = self.tail
# remove tail
self.tail = tail.pre
self.tail.next = None
# move to head
tail.next = head
tail.pre = head.pre
self.head = tail
def rotate_head_to_tail(self) -> None:
"""[反向旋转节点]
移动头点，插入到尾部
"""
assert self.len >= 2, "dlist len must >=2"
head = self.head
tail = self.tail
# remove head
self.head = head.next
self.head.pre = None
# move to tail
tail.next = head
head.pre = tail
self.tail = head
self.tail.next = None
def join(self, dlist: Any=None):
"""[合并双链表]
Args:
dlist (Any, optional): [description]. Defaults to None.
"""
pass
def __str__(self) -> str:
ans = ""
for idx, node in self.next(reversed=False):
ans += f"idx:({idx}) data:({node.data})n"
return ans
def test_add_node(dlist:DLinkList=None):
n = 5
for i in range(n):
dlist.add_node_tail(data=i)
# dlist.add_node_head(data=i)
print(dlist)
def test_del_node(dlist:DLinkList=None):
i = dlist.len
while i:
node = None
dlist.del_node(node)
i -= 1
print(dlist)
def test_insert_node(dlist:DLinkList=None):
# dlist.insert_node(old_node=old_node, data=100, after=True)
# print(dlist, id(dlist))
# nlist = dlist.dup()
# print(nlist, id(nlist))
idx, fnode = dlist.find(1)
print('find node:', idx, fnode)
dlist.insert_node(fnode, 100, after=True)
print("insert after")
print(dlist)
dlist.insert_node(fnode, 200, after=False)
print("insert before")
print(dlist)
def test_rotate(dlist:DLinkList=None):
print("move head to tail")
dlist.rotate_head_to_tail()
print(dlist)
print("move tail to head")
dlist.rotate_tail_to_head()
print(dlist)
def test_join(dlist:DLinkList=None, olist:DLinkList=None):
print("join list")
nlist = dlist.join(olist)
print(nlist)
def main():
dlist = DLinkList()
test_add_node(dlist)
# test_del_node(dlist)
# test_insert_node(dlist)
test_rotate(dlist)
if __name__ == "__main__":
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