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单链表(python)

# -*- coding: utf-8 -*-


class Node(object):
def __init__(self, value=None, next=None): # 这里我们 root 节点默认都是 None,所以都给了默认值
self.value = value
self.next = next

def __str__(self):
"""方便你打出来调试,复杂的代码可能需要断点调试"""
return '<Node: value: {}, next={}>'.format(self.value, self.next)

__repr__ = __str__


class LinkedList(object):
""" 链接表 ADT
[root] -> [node0] -> [node1] -> [node2]
"""

def __init__(self, maxsize=None):
"""
:param maxsize: int or None, 如果是 None,无限扩充
"""
self.maxsize = maxsize
self.root = Node() # 默认 root 节点指向 None
self.tailnode = None
self.length = 0

def __len__(self):
return self.length

def append(self, value): # O(1)
if self.maxsize is not None and len(self) >= self.maxsize:
raise Exception('LinkedList is Full')
node = Node(value) # 构造节点
tailnode = self.tailnode
if tailnode is None: # 还没有 append 过,length = 0, 追加到 root 后
self.root.next = node
else: # 否则追加到最后一个节点的后边,并更新最后一个节点是 append 的节点
tailnode.next = node
self.tailnode = 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)
if self.tailnode is None: # 如果原链表为空,插入第一个元素需要设置 tailnode
self.tailnode = node

headnode = self.root.next
self.root.next = node
node.next = headnode
self.length += 1

def __iter__(self):
for node in self.iter_node():
yield node.value

def iter_node(self):
"""遍历 从 head 节点到 tail 节点"""
curnode = self.root.next
while curnode is not self.tailnode: # 从第一个节点开始遍历
yield curnode
curnode = curnode.next # 移动到下一个节点
if curnode is not None:
yield curnode

def remove(self, value): # O(n)
""" 删除包含值的一个节点,将其前一个节点的 next 指向被查询节点的下一个即可

:param value:
"""
prevnode = self.root #
for curnode in self.iter_node():
if curnode.value == value:
prevnode.next = curnode.next
if curnode is self.tailnode: # NOTE: 注意更新 tailnode
self.tailnode = prevnode
del curnode
self.length -= 1
return 1 # 表明删除成功
else:
prevnode = curnode
return -1 # 表明删除失败

def find(self, value): # O(n)
""" 查找一个节点,返回序号,从 0 开始

:param value:
"""
index = 0
for node in self.iter_node(): # 我们定义了 __iter__,这里就可以用 for 遍历它了
if node.value == value:
return index
index += 1
return -1 # 没找到

def popleft(self): # O(1)
""" 删除第一个链表节点
"""
if self.root.next is None:
raise Exception('pop from empty LinkedList')
headnode = self.root.next
self.root.next = headnode.next
self.length -= 1
value = headnode.value

if self.tailnode is headnode: # 勘误:增加单节点删除 tailnode 处理
self.tailnode = None
del headnode
return value

def clear(self):
for node in self.iter_node():
del node
self.root.next = None
self.length = 0
self.tailnode = None

def reverse(self):
"""反转链表"""
curnode = self.root.next
self.tailnode = curnode # 记得更新 tailnode,多了这个属性处理起来经常忘记
prevnode = None

while curnode:
nextnode = curnode.next
curnode.next = prevnode

if nextnode is None:
self.root.next = curnode

prevnode = curnode
curnode = nextnode


def test_linked_list():
ll = LinkedList()

ll.append(0)
ll.append(1)
ll.append(2)
ll.append(3)

assert len(ll) == 4
assert ll.find(2) == 2
assert ll.find(-1) == -1

assert ll.remove(0) == 1
assert ll.remove(10) == -1
assert ll.remove(2) == 1
assert len(ll) == 2
assert list(ll) == [1, 3]
assert ll.find(0) == -1

ll.appendleft(0)
assert list(ll) == [0, 1, 3]
assert len(ll) == 3

headvalue = ll.popleft()
assert headvalue == 0
assert len(ll) == 2
assert list(ll) == [1, 3]

assert ll.popleft() == 1
assert list(ll) == [3]
ll.popleft()
assert len(ll) == 0
assert ll.tailnode is None

ll.clear()
assert len(ll) == 0
assert list(ll) == []


def test_linked_list_remove():
ll = LinkedList()
ll.append(3)
ll.append(4)
ll.append(5)
ll.append(6)
ll.append(7)
ll.remove(7)
print(list(ll))


def test_linked_list_reverse():
ll = LinkedList()
n = 10
for i in range(n):
ll.append(i)
ll.reverse()
assert list(ll) == list(reversed(range(n)))


def test_linked_list_append():
ll = LinkedList()
ll.appendleft(1)
ll.append(2)
assert list(ll) == [1, 2]


if __name__ == '__main__':
test_linked_list()
test_linked_list_append()
test_linked_list_reverse()

 

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