单向循环链表之python

class Node(object):
    def __init__(self,elem):
        self.elem = elem
        self.next = None
class SingleLinkCir(object):
    def __init__(self,node=None):

        self.__head = node
        if node:

            self.node = node #节点默认指向自己
    def is_empty(self):
        return self.__head == None
        """遍历所有节点，并记录数据"""
    def length(self):
        if self.is_empty():
            return 0
        cur = self.__head
        count = 1
        while cur.next != self.__head:#跳出循环条件,当当当前指针的下一指针指向头结点时证明此节点为为尾节点
            cur = cur.next
            count += 1
        return count
    
    def travel(self):
        cur = self.__head
        if self.__head == None:
            return None
        else:
            while cur.next != self.__head:            
                print(cur.elem,end="")
                cur = cur.next
            print(cur.elem)#当cur等于尾节点时，退出循环，但是尾节点的元素需要打印，所以退出循环时候进行打印    
        
    def add(self,item):
        node = Node(item)
        if self.is_empty():#判断链表是否为空
            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 = node
    def append(self,item):
        node = Node(item)
        #cur = self.__head
        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.next
            node.next = self.__head
            cur.next = node
    def insert(self,pos,item):
        if pos <= 0:
            self.add(item)
        elif pos > (self.length()-1):
            self.append(item)
        else:
            node = Node(item)
            cur = self.__head
            count = 0
            if is_empty():
                self.__head == node
                node.next = node
            else:
                while count < pos:
                    cur = cur.next
                    count += 1
                node.next = cur.next
                cur.next = node
    def search(self,item):
        cur = self.__head
        if self.is_empty():
            return False
        while cur.elem != item:
            if cur.next !=self.__head:
                
                cur = cur.next
            else:
                return False
        return True
            
    def remove(self,item):
        if self.is_empty():
            return 
        cur = self.__head
        pre = None

        while cur.elem != item:
            if cur.next != self.__head:
                pre = cur
                cur = cur.next
            
            else:
                return False
        
        if cur == self.__head:#如果删除的是头结点，要找到尾节点，把尾节点的指向改为原来头结点的next
            if self.length() != 1:#判段链表中是否只有一个节点,只有一个节点则引入尾节点，
                rear_node = self.__head
                while rear_node.next != self.__head:
                    rear_node = rear_node.next
            #pre.next = self.__head
                self.__head = cur.next
                rear_node.next = self.__head
        #    rear.next = cur.next
        #    self.__head= cur.next
            else:#只有一个节点，删除唯一节点，
                self.__head = None
        else:#删除中间节点和尾节点

            pre.next = cur.next


if __name__ == "__main__":
    ll= SingleLinkCir()
    print(ll.is_empty())
    print(ll.length())
    

    ll.append(1)
    print(ll.is_empty())
    print(ll.length())
#    ll.travel()
    print("*" * 50)

    ll.remove(1)
    ll.append(2)
    ll.add(8)
    ll.insert(3,3)
    ll.travel()
    ll.append(100)
    ll.travel()
    ll.remove(100)
    ll.travel()
    ll.remove(8)
    ll.travel()