class Node(object):
def __init__(self, elem):
"""
:param elem: 表元素域
next：下一结点链接域
cursor(cur)：游标
"""
self.elem = elem
# 定义next指向空
self.next = None
class SingleCircularLinkList(object):
"""
单向循环链表：单链表的一个变形是单向循环链表，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
"""
def __init__(self, node=None):
self.__head = node # node.elem node.next
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():
return 0
# cur游标，用来移动遍历节点
cur = self.__head
count = 1
while cur.next != self.__head:
count += 1
cur = cur.next
# count 记录数量
return count
def travel(self):
"""遍历整个链表"""
if self.is_empty():
return
cur = self.__head
while cur.next != self.__head:
print(cur.elem, end=' ')
cur = cur.next
# 退出循环，cur指向尾结点，但尾节点的元素未打印
print(cur.elem)
def add(self, item):
"""链表头部添加元素：头插法"""
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
# 退出循环，cur指向尾结点
node.next = self.__head
self.__head = node
# 方式1：cur.next = node
cur.next = self.__head # 方式2
def append(self, item):
"""链表尾部添加元素:尾插法"""
node = Node(item)
# 下一结点链接域不为空
if self.is_empty():
self.__head = node
node.next = node
else:
cur = self.__head
while cur.next != self.__head:
cur = cur.next
# 方式1：
# node.next = cur.next
# cur.next = node
# 方式2：
cur.next = node
node.next = self.__head
def insert(self, pos, item):
"""
pos: pos从0开始
pre:指定节点前一节点，相当于游标
node：插入的指定节点
指定位置添加元素
"""
# if pos<=0 头插法
if pos <= 0:
self.add(item)
# elif pos>(self.length()-1) 尾插法
elif pos > (self.length() - 1):
self.append(item)
# else 插入法
else:
pre = self.__head
count = 0
# 当循环退出后，pre指向pos-1
while count < (pos - 1):
count += 1
pre = pre.next
node = Node(item)
node.next = pre.next
pre.next = node
def remove(self, item):
"""删除元素"""
# 考虑删除头部、尾部、中间节点
if self.is_empty():
return
cur = self.__head
pre = None
while cur.next != self.__head:
if cur.elem == item:
# 先判断是否是头节点
if cur == self.__head:
# 找到尾节点
rear = self.__head
while rear.next != self.__head:
rear = rear.next
self.__head = cur.next
rear.next = self.__head
else:
# 中间节点
pre.next = cur.next
return
else:
pre = cur
cur = cur.next
# 退出循环，cur指向尾结点
if cur.elem == item:
if cur == self.__head:
# 链表只有一个节点
self.__head = None
else:
pre.next = cur.next
def search(self, item):
"""查找节点是否存在"""
if self.is_empty():
return False
# 1. 创建游标
cur = self.__head
# 2. 遍历游标
while cur.next != self.__head:
# 3. cur.elem = item
if cur.elem == item:
return True
else:
cur = cur.next
# 对于最后一个元素或只有一个元素
if cur.elem == item:
return True
return False
if __name__ == '__main__':
ll = SingleCircularLinkList()
ll.is_empty()
l1 = ll.length()
print(l1)
ll.append(55)
ll.is_empty()
l2 = ll.length()
print(l2)
ll.append(2)
ll.add(8)
ll.append(3)
ll.append(4)
ll.append(5)
# 55 1 8 2 3 4
ll.insert(-1,9) # 9 8 55 2 1 8 2345
ll.insert(2,100) #9 8 100 55 2 1 8 2345
ll.travel()
