python实现单向循环链表

废话不多说，直接上代码：

#-*-coding=utf-8-*-
class Node(object):
    """节点"""
    def __init__(self,elem):
        self.elem=elem
        self.next=None

class SingleCircleLink(object):
    """单链表"""
    def __init__(self,node=None):
        self.__head = node
        if node:
            node.next=node

    def is_empty(self):
        """判断是否为空"""
        return self.__head==None

    def length(self):
        """链表长度"""
        if self.__head==None:
            return 0
        #cur游标，用来移动遍历节点
        cur = self.__head
        #count记录数量
        count=1
        while cur.next!=self.__head:
            cur=cur.next
            count+=1
        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)
            cur=cur.next
        print(cur.elem)

    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:
            cur=self.__head
            while cur.next!=self.head:
                cur=cur.next
            node.next=self.__head
            self.__head=node
            cur.next=self.__head


    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:
            cur=self.__head
            while cur.next!=self.__head:
                cur=cur.next
            cur.next=node
            node.next = self.__head


    def insert(self,pos,item):
        """指定位置添加元素"""
        if pos<=0:
            self.add(item)
        elif pos>self.length()-1:
            self.append(item)
        else:
            pre=self.__head
            count=0
            while count<pos-1:
                pre=pre.next
                count+=1
            Node(item).next=pre.next
            pre.next=Node(item)

    def remove(self,item):
        """删除节点"""
        if self.is_empty():
            return
        cur=self.__head
        pre=None
        while cur.next!=self.__head:
            if cur.elem==item:
                if cur==self.__head:
                    rear=self.__head
                    while rear.next!=self.__head:
                        rear=cur.next
                    self.__head=cur.next
                    rear.next=self.__head
                pre.next=cur.next
            else:
                pre=cur
                cur=cur.next

    def search(self,item):
        """查找节点是否存在"""
        if self.is_empty():
            return False
        else:
            cur=self.__head
            while cur.next!=self.__head:
                if cur.elem==item:
                    return True
                else:
                    cur=cur.next
            if cur.elem==item:
                return True
            return False


if __name__=="__main__":
    ll=SingleCircleLink()
    print(ll.is_empty())
    print(ll.length())
    ll.append(1)
    ll.append(2)
    ll.append(3)
    ll.append(4)
    ll.append(5)
    ll.append(6)
    ll.append(7)
    print(ll.is_empty())
    print(ll.length())
    ll.travel()