python单向循环链表原理与实现方法示例

本文实例讲述了python单向循环链表原理与实现方法。分享给大家供大家参考，具体如下：单

本文实例讲述了python单向循环链表原理与实现方法。分享给大家供大家参考，具体如下：

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。

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

实现

# -*- coding:utf-8 -*-
#! python3
class Node(object):
 """节点"""
 def __init__(self, item):
 self.item = item
 self.next = None
class SinCycLinkedlist(object):
 """单向循环链表"""
 def __init__(self):
 self.__head = None
 def is_empty(self):
 """判断链表是否为空"""
 return self.__head == None
 def length(self):
 """返回链表的长度"""
 # 如果链表为空，返回长度0
 if self.is_empty():
 return 0
 count = 1
 cur = self.__head
 while cur.next != self.__head:
 count += 1
 cur = cur.next
 return count
 def travel(self):
 """遍历链表"""
 if self.is_empty():
 return
 cur = self.__head
 print(cur.item,)
 while cur.next != self.__head:
 cur = cur.next
 print(cur.item,)
 print("")
 def add(self, item):
 """头部添加节点"""
 node = Node(item)
 if self.is_empty():
 self.__head = node
 node.next = self.__head
 else:
 # 添加的节点指向_head
 node.next = self.__head
 # 移到链表尾部，将尾部节点的next指向node
 cur = self.__head
 while cur.next != self.__head:
 cur = cur.next
 cur.next = node
 # _head指向添加node的
 self.__head = node
 def append(self, item):
 """尾部添加节点"""
 node = Node(item)
 if self.is_empty():
 self.__head = node
 node.next = self.__head
 else:
 # 移到链表尾部
 cur = self.__head
 while cur.next != self.__head:
 cur = cur.next
 # 将尾节点指向node
 cur.next = node
 # 将node指向头节点_head
 node.next = self.__head
 def insert(self, pos, item):
 """在指定位置添加节点"""
 if pos <= 0:
 self.add(item)
 elif pos > (self.length() - 1):
 self.append(item)
 else:
 node = Node(item)
 cur = self.__head
 count = 0
 # 移动到指定位置的前一个位置
 while count < (pos - 1):
 count += 1
 cur = cur.next
 node.next = cur.next
 cur.next = node
 def remove(self, item):
 """删除一个节点"""
 # 若链表为空，则直接返回
 if self.is_empty():
 return
 # 将cur指向头节点
 cur = self.__head
 pre = None
 while cur.next != self.__head:
 if cur.item == item:
 # 先判断此结点是否是头节点
 if cur == self.__head:
 # 头节点的情况
 # 找尾节点
 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指向尾节点
 if cur.item == item:
 if cur == self.__head:
 # 链表只有一个节点
 self.__head = None
 else:
 # pre.next = cur.next
 pre.next = self.__head
 def search(self, item):
 """查找节点是否存在"""
 if self.is_empty():
 return False
 cur = self.__head
 if cur.item == item:
 return True
 while cur.next != self.__head:
 cur = cur.next
 if cur.item == item:
 return True
 return False
if __name__ == "__main__":
 ll = SinCycLinkedlist()
 ll.add(1)
 ll.add(2)
 ll.append(3)
 ll.insert(2, 4)
 ll.insert(4, 5)
 ll.insert(0, 6)
 print("length:", ll.length())
 ll.travel()
 print(ll.search(3))
 print(ll.search(7))
 ll.remove(1)
 print("length:", ll.length())
 ll.travel()

运行结果：

length: 6 6 2 1 4 3 5

True False length: 5 6 2 4 3 5

python 单向循环链表