Python数据结构——链表（三）环链表

尾结点指向头结点为环链表

class node(object):
    def __init__(self,item):
        self.item = item
        self.next = None
    
class circlechainlist(object):
    def __init__(self,length = 10):
        self.length = length
        self.head = node(None)
        self.head.next = self.head
        self.count = 0
        
    def __num_node(self,x:int):
        self.count += x
    
    def search(self,x:node): # search for the node and return the precvious node
        if self.head.next == x:
            return self.head
        else:
            temp = self.head.next
            while temp.next != x:
                temp = temp.next
            return temp
        
    def add_node(self,node:node): # add at the end of chain
        if self.count == self.length:
            print('cannot exceed max length')
        else:
            self.find_tail().next = node
            node.next = self.head
            self.__num_node(1)
            
    def find_tail(self,x=None): # find the last node
        if x is None:
            x = self.head
        if x.next == self.head:
            return x
        else:
            temp = x.next
            if temp.next == self.head:
                return temp
            else:
                return self.find_tail(temp)
    
    def del_node(self,x=None):
        if self.head.next == self.head:
            print('no node any more!')
        else:
            if x is None:
                self.search(self.find_tail()).next=None
                self.__num_node(-1)
            else:
                self.search(x).next = x.next
                x = None
                self.__num_node(-1)
    
    def insert_node(self,x:node,y:node):
        if self.count == self.length:
            print('cannot exceed max length')
        else:
            if self.head.next == self.head:
                self.head.next = y
                y.next = self.head
                self.__num_node(1)
            else:
                self.search(x).next = y
                y.next = x
                self.__num_node(1)
            
    def get_chain(self):
        chain = [self.head]
        while chain[-1].next != self.head:
            chain.append(chain[-1].next)
        return chain