单循环链表

class Node():
    def __init__(self,item):
        self.item=item
        self.next=None
class CycleSingleLinkList():
    def __init__(self,node=None):
        self.__head=node
    def is_empty(self):
        return self.__head is None
    def length(self):
        if self.is_empty():
            return 0
        count=1
        cur=self.__head
        while cur.next is not self.__head:
            count+=1
            cur=cur.next
        return count
    def travel(self):
        if self.is_empty():
            print('')
            return
        cur=self.__head
        while cur.next is not self.__head:
            print(cur.item,end='')
            cur=cur.next
        print(cur.item)
    def search(self,item):
        if self.is_empty():
            return False
        cur=self.__head
        while cur.next is not self.__head:
            if cur.item==item:
                return True
            cur=cur.next
        if cur.item==item:
            return True
        return False
    def add(self,item):
        node=Node(item)
        if self.is_empty():
            self.__head=node
            node.next=self.__head
        cur=self.__head
        while cur.next is not self.__head:
            cur=cur.next
        cur.next=node
        node.next=self.__head
        self.__head=node
    def append(self,item):
        node=Node(item)
        if self.is_empty():
            self.__head = node
            node.next=self.__head
        cur=self.__head
        while cur.next is not self.__head:
            cur=cur.next
        cur.next=node
        node.next=self.__head
    def insert(self,pos,item):
        node=Node(item)
        if pos<=0:
            self.add(item)
        elif pos>self.length():
            self.append(item)
        else:
            cur=self.__head
            count=0
            while count<(pos-1):
                cur=cur.next
                count+=1
            node.next=cur.next
            cur.next=node
    def remove(self,item):
        if self.is_empty():
            return
        cur=self.__head
        pre=None
        while cur.next is not self.__head:
            if cur.item==item:
                if cur==self.__head:
                    tnode=self.__head
                    while tnode.next is not self.__head:
                        tnode=tnode.next
                    self.__head=cur.next
                    tnode.next=self.__head
                else:
                    pre.next=cur.next
                    return
            pre=cur
            cur=cur.next
        if cur.item==item:
            if cur==self.__head:
                self.__head=None
            else:
                pre.next=self.__head

if __name__ == '__main__':
    cc=CycleSingleLinkList()
    for i in range(10):
        cc.append(i)
    cc.travel()
    print(cc.length())
    cc.add(1)
    cc.travel()
    cc.insert(2,3)
    cc.travel()
    cc.remove(3)
    cc.travel()