python 单向循环列表

 # -*- coding: utf-8 -*-
 # @author: Tele
 # @Time  : 2019/04/23 下午 6:54
 # 单向循环列表
 # 单向循环列表与单向列表的不同之处在于最后一个元素的next为头节点
 class SingleCycleNode:
     def __init__(self, data, next=None):
         self.data = data
         # next指向下一个节点而不是数据
         self.next = next

 # 使用链表时只需要传入待存储的数据而不是节点
 class SingleCycleLinkedList:
     def __init__(self, data=None):
         node = SingleCycleNode(data)
         self.__head = node if node.data else None
         if self.__head:
             self.__head.next = node

     def is_empty(self):
         return self.__head == None

     def length(self):
         count = 0
         if self.is_empty():
             return count
         cur = self.__head
         if cur:
             while cur.next is not self.__head:
                 count += 1
                 cur = cur.next
         return count + 1

     # 头部添加元素
     def add(self, data):
         node = SingleCycleNode(data)
         if self.is_empty():
             self.__head = node
             self.__head.next = node
         else:
             node.next = self.__head
             cur = self.__head
             while cur.next is not self.__head:
                 cur = cur.next
             # 此时cur为尾节点
             cur.next = node
             self.__head = node

     # 尾部添加元素
     def append(self, data):
         node = SingleCycleNode(data)
         if self.is_empty():
             self.__head = node
             self.__head.next = node
         else:
             node.next = self.__head
             cur = self.__head
             while cur.next is not self.__head:
                 cur = cur.next
             cur.next = node

     # 指定位置插入
     def insert(self, pos, data):
         node = SingleCycleNode(data)
         cur = self.__head
         count = 0
         if self.length() >= pos >= 0:
             while cur.next is not self.__head:
                 if count + 1 == pos:
                     node.next = cur.next
                     cur.next = node
                     break
                 # pos为0
                 elif count == pos:
                     self.add(data)
                     break
                 count += 1
                 cur = cur.next
         elif pos < 0:
             self.add(data)
         else:
             self.append(data)
         # 如果列表中插入时没有元素
         if not self.__head:
             self.append(data)

     # 遍历
     def travel(self):
         cur = self.__head
         while cur and cur.next is not self.__head:
             print(cur.data)
             cur = cur.next
         print(cur.data if cur else "")

     # 移除出现的第一个元素
     def remove(self, data):
         if self.is_empty():
             return
         node = self.__find(data)
         cur = self.__head
         # 头节点
         if self.__head.data == node.data:
             while cur.next is not self.__head:
                 cur = cur.next
             self.__head = node.next
             cur.next = self.__head
         # 尾节点,普通位置节点
         else:
             cur = self.__head
             while cur.next and cur.next is not self.__head:
                 if cur.next.data == node.data:
                     break
                 cur = cur.next
             cur.next = node.next

     # 私有方法,用于查找节点
     def __find(self, data):
         cur = self.__head
         node = SingleCycleNode(data)
         while cur and cur.next is not self.__head:
             if cur.data == data:
                 node.next = cur.next
                 break
             cur = cur.next
         # 如果是尾节点
         if cur and cur.data == data:
             node.next = cur.next
         return node

     # 查找,找不到返回-1,找到则返回索引
     def search(self, data):
         index = -1
         cur = self.__head
         count = 0
         while cur and cur.next is not self.__head:
             if cur.data == data:
                 index = count
                 break
             count += 1
             cur = cur.next
         # 如果是尾节点
         if cur and cur.data == data:
             index = count
         return index

 def main():
     scll = SingleCycleLinkedList()
     print(scll.is_empty())
     print(scll.length())
     scll.add(1)
     scll.add(2)
     scll.append(10)
     scll.append(10)
     scll.append(100)
     print(scll.is_empty())
     print(scll.length())
     # print("*" * 50)
     # scll.travel()
     print("*" * 50)
     scll.insert(-1, 1000)
     print("search", scll.search(10))
     scll.travel()
     print("*" * 50)
     scll.remove(10)
     scll.travel()

 if __name__ == '__main__':
     main()