4. 单向循环链表
单向循环链表是单链表的一个变形,链表中最后一个节点的next域不再为None,而是指向链表的头节点。
4.1 节点实现
class Node(object):
def __init__(self, elem):
self.elem = elem
self.next = None
4.2 链表实现
- 单向循环链表可执行的操作
is_empty() 判断链表是否为空
length() 返回链表的长度
travel() 遍历
add(item) 在头部添加一个节点
append(item) 在尾部添加一个节点
insert(pos, item) 在指定位置pos添加节点
remove(item) 删除一个节点
search(item) 查找节点是否存在 - 代码实现
class SingleCycleLinkList(object):
def __init__(self, node=None):
self.__head = node
if node:
node.next = node
def is_empty(self):
"""链表是否为空"""
return self.__head is None
def length(self):
"""链表长度"""
if self.is_empty(): # 判断链表是否为空
return 0
cursor = self.__head
count = 1
while cursor.next != self.__head:
count += 1
cursor = cursor.next
return count
def travel(self):
"""遍历整个链表"""
if self.is_empty():
return
cursor = self.__head
while cursor.next != self.__head:
print(cursor.elem, end='\t')
cursor = cursor.next
# 退出循环,cursor指向尾结点,但尾结点的元素未打印
print(cursor.elem)
print("")
def add(self, item):
"""链表头部添加元素"""
node = Node(item)
if self.is_empty():
self.__head = node
node.next = node
else:
cursor = self.__head
while cursor.next != self.__head:
cursor = cursor.next
# 退出循环,cursor指向尾结点
node.next = self.__head
self.__head = node
cursor.next = node
def append(self, item):
"""链表尾部添加元素"""
node = Node(item)
if self.is_empty():
self.__head = node
node.next = node
else:
cursor = self.__head
while cursor.next != self.__head:
cursor = cursor.next
# 退出循环,cursor指向尾结点
cursor.next = node
node.next = self.__head
def insert(self, pos, item):
"""指定位置添加元素
:param pos 从0开始
"""
if pos <= 0:
self.add(item)
elif pos > self.length()-1:
self.append(item)
else:
node = Node(item)
prior = self.__head
count = 0
while count < pos-1:
prior = prior.next
count += 1
# 当循环退出后,prior指向pos-1的位置
node.next = prior.next
prior.next = node
def remove(self, item):
"""删除节点"""
if self.is_empty():
return
cursor = self.__head
prior = None
while cursor.next != self.__head:
if cursor.elem == item:
# 先判断是否是头节点
if cursor == self.__head:
# 头节点
# 先找尾结点
rear = self.__head
while rear.next != self.__head:
rear = rear.next
# 达到尾结点
self.__head = cursor.next
rear.next = self.__head
else:
# 中间节点
prior.next = cursor.next
return
else:
prior = cursor
cursor = cursor.next
# 退出循环,cursor指向尾部
# 尾结点
if cursor.elem == item:
if prior:
prior.next = cursor.next
else:
self.__head = None
def search(self, item):
"""查找节点是否存在"""
if self.is_empty():
return False
cursor = self.__head
while cursor.next != self.__head:
if cursor.elem == item:
return True
else:
cursor = cursor.next
# 退出循环,cursor指向尾结点
if cursor.elem == item:
return True
return False