python遍历链表_四种常见链表的实现及时间复杂度分析（Python3版）

class Node(object):

"""单节点"""

def __init__(self, elem):

self.elem = elem

self.next = None

class DoubleNode(Node):

"""双节点"""

def __init__(self, elem):

super(DoubleNode, self).__init__(elem)

self.prev = None

class SingleLinkList(object):

"""单链表"""

def __init__(self, node=None):

self.head = node

def is_empty(self) -> bool:

"""链表是否为空 O(1)"""

return self.head is None

def length(self) -> int:

"""链表长度 O(n)"""

count, cur = 0, self.head

while cur is not None:

cur = cur.next # 不要写错cur = self.head.next, self.__next不是活动指针

count += 1

return count

def traversing(self) -> '':

"""遍历所有节点 O(n)"""

cur = self.head # 不是 self._head

while cur is not None:

print(cur.elem, end=' ')

cur = cur.next

return ''

def add(self, item) -> None:

"""头部添加节点 O(1)"""

node = Node(item)

node.next = self.head

self.head = node

def append(self, item) -> None:

"""尾部添加节点 O(n)"""

node = Node(item)

cur = self.head

if self.is_empty():

self.head = node

else:

while cur.next is not None:

cur = cur.next

cur.next = node

def insert(self, position: int, item) -> None:

"""

节点插入到某个位置 O(n)

:param position: 0表示第1个位置

:param item:

:return: None

"""

if position <= 0:

self.add(item)

elif position >= self.length():

self.append(item)

else:

node = Node(item)

count, cur = 1, self.head

while count < position:

cur = cur.next

count += 1

node.next = cur.next

cur.next = node

def remove(self, item) -> None:

"""删除链表中的一个节点 O(n)"""

pre, cur = None, self.head

while cur is not None:

if cur.elem == item:

if cur == self.head:

self.head = cur.next

break # 只remove第一个元素

pre.next = cur.next

break

pre = cur

cur = cur.next

def search(self, item) -> bool:

"""查找节点是否存在 O(n)"""

cur = self.head

while cur is not None:

if cur.elem == item:

return True

cur = cur.next

return False

class SingleCycleLinkList(SingleLinkList):

"""单向循环链表"""

def __init__(self, node=None):

if node:

node.next = node

super(SingleCycleLinkList, self).__init__(node=node)

def length(self) -> int:

"""链表长度 O(n)"""

if self.is_empty():

return 0

count, cur = 1, self.head

while cur.next != self.head:

cur = cur.next # 不要写错cur = self.head.next, self.__next不是活动指针

count += 1

return count

def traversing(self) -> '':

"""遍历所有节点 O(n)"""

if not self.is_empty():

cur = self.head # 不是 self._head

while cur.next != self.head:

print(cur.elem, end=' ')

cur = cur.next

print(cur.elem, end=' ')

return ''

def add(self, item) -> None:

"""头部添加节点 O(n)"""

node = Node(item)

if self.is_empty():

self.head = node

node.next = node

else:

cur = self.head

while cur.next != self.head:

cur = cur.next

# 退出while循环之后cur指向尾结点

node.next = self.head

self.head = node

cur.next = self.head

def append(self, item) -> None:

"""尾部添加节点 O(n)"""

node = Node(item)

if self.is_empty():

self.head = node

node.next = node

else:

cur = self.head

while cur.next != self.head:

cur = cur.next

cur.next = node

node.next = self.head

def insert(self, position: int, item) -> None:

"""

节点插入到某个位置 O(n)

:param position: 0表示第1个位置

:param item:

:return: None

"""

if position <= 0:

self.add(item)

elif position >= self.length():

self.append(item)

else:

node = Node(item)

count, cur = 1, self.head

while count < position:

cur = cur.next

count += 1

node.next = cur.next

cur.next = node

def remove(self, item) -> None:

"""删除链表中的一个节点 O(n)"""

if self.is_empty():

return

pre, cur = None, self.head

while cur.next != self.head:

if cur.elem == item:

# 移除头结点

if cur == self.head:

rear = self.head

while rear.next != self.head:

rear = rear.next

self.head = cur.next

rear.next = self.head

# 移除中间节点

else:

pre.next = cur.next

return # 结束。只remove第一个元素

pre = cur

cur = cur.next

# 移除尾结点

if cur.elem == item:

if cur == self.head:

self.head = None

else:

pre.next = self.head # 或者 pre.next = cur.next

def search(self, item) -> bool:

"""查找节点是否存在 O(n)"""

if self.is_empty():

return False

else:

cur = self.head

while cur.next != self.head:

if cur.elem == item:

return True

cur = cur.next

return cur.elem == item

class DoubleLinkList(SingleLinkList):

"""双链表"""

def add(self, item) -> None:

"""头部添加节点 O(1)"""

node = DoubleNode(item)

node.next = self.head

self.head = node

if node.next: # 当原链表为空时

node.next.prev = node

def append(self, item) -> None:

"""尾部添加节点 O(n)"""

node = DoubleNode(item)

cur = self.head

if self.is_empty():

self.head = node

else:

while cur.next is not None:

cur = cur.next

cur.next = node

node.prev = cur

def insert(self, position: int, item) -> None:

"""

节点插入到某个位置 O(n)

:param position: 0表示第1个位置

:param item:

:return: None

"""

if position <= 0:

self.add(item)

elif position >= self.length():

self.append(item)

else:

node = DoubleNode(item)

count, cur = 1, self.head

while count < position:

cur = cur.next

count += 1

node.next = cur.next

node.prev = cur

cur.next.prev = node

cur.next = node

def remove(self, item) -> None:

"""删除链表中的一个节点 O(n)"""

cur = self.head

while cur is not None:

if cur.elem == item:

if cur == self.head:

self.head = cur.next

if self.head: # 只有一个节点的特殊情况

cur.next.prev = None

else:

cur.prev.next = cur.next

if cur.next:

cur.next.prev = cur.prev

break # 只remove第一个元素

cur = cur.next

class DoubleCycleLinkList(SingleCycleLinkList):

"""双向循环链表"""

def __init__(self, node=None):

if node:

node.next = node

node.prev = node

super(DoubleCycleLinkList, self).__init__(node=node)

def add(self, item) -> None:

"""头部添加节点 O(n)"""

node = DoubleNode(item)

if self.is_empty():

self.head = node

node.next = node

node.prev = node

else:

cur = self.head

while cur.next != self.head:

cur = cur.next

# 退出while循环之后cur指向尾结点，双向循环链表需要改动5个指针

node.next = self.head # 1.node.next指向原来的头结点

node.prev = cur # 2.node.prev指向尾结点，当前cur指向的节点

cur.next.prev = node # 3.原来头结点的prev指向要插入的node

self.head = node # 4.self.head指向要插入的node

cur.next = node # 5.尾结点的next指向要插入的node

def append(self, item) -> None:

"""尾部添加节点 O(n)"""

node = DoubleNode(item)

if self.is_empty():

self.head = node

node.next = node

node.prev = node

else:

cur = self.head

# 退出while循环之后cur指向尾结点，双向循环链表需要改动4个指针

while cur.next != self.head:

cur = cur.next

cur.next.prev = node # 1.原来头结点的.prev指向要插入的node

cur.next = node # 2.原来尾结点.next指向要插入的node

node.prev = cur # 3.node.prev指向原来的尾节点

node.next = self.head # 4.node.next指向头结点

def insert(self, position: int, item) -> None:

"""

节点插入到某个位置 O(n)

:param position: 0表示第1个位置

:param item:

:return: None

"""

if position <= 0:

self.add(item)

elif position >= self.length():

self.append(item)

else:

node = DoubleNode(item)

count, cur = 1, self.head

while count < position:

cur = cur.next

count += 1

node.next = cur.next

node.prev = cur

cur.next.pre = node

cur.next = node

def remove(self, item) -> None:

"""删除链表中的一个节点 O(n)"""

if self.is_empty():

return

cur = self.head

while cur.next != self.head:

if cur.elem == item:

# 移除头结点

if cur == self.head:

cur.prev.next = cur.next

cur.next.prev = cur.prev

self.head = cur.next

# 移除中间节点

else:

cur.prev.next = cur.next

cur.next.prev = cur.prev

return # 结束。只remove第一个元素

cur = cur.next

# 移除尾结点

if cur.elem == item:

if cur == self.head: # 当链表只有一个节点时

self.head = None

else:

cur.next.prev = cur.prev

cur.prev.next = cur.next

if __name__ == '__main__':

print("----single_link_list-----")

single_link_list = SingleLinkList()

single_link_list.remove('test')

print(single_link_list.is_empty(), single_link_list.length())

single_link_list.insert(-1, 'zhao')

print(single_link_list.is_empty(), single_link_list.length())

single_link_list.insert(3, 'zi')

print(single_link_list.length())

single_link_list.append('yang')

single_link_list.add("head")

single_link_list.insert(4, "tail")