python 链表

# encoding=utf-8

class Node():
    def __init__(self, data,p=0):
        self.data = data
        self.next = p

class linkList():
    def __init__(self):
        self.length = 0
        self.head = 0
    '''
      判断链表是否为空
    '''
    def is_empty(self):
        return self.length == 0
    '''
      链表长度
    '''
    def length(self):
        current = self.head
        if current:
            i = 1
            while current.next:
                current = current.next
                i += 1
            return i
        else:
            return 0
    '''
      打印链表
    '''
    def print_link(self):
        if self.is_empty():
            print('empty')
        else:
            node = self.head
            print('head',node.data)
            while node.next:
                node = node.next
                print(node.data)
    '''
      链表末尾添加node
    '''
    def append_node(self, this_node):
        if self.is_empty():
            '''
             链表为空，head指向node 
           '''
            self.head = this_node
        else:
            node = self.head
            while node.next:
                node = node.next
            node.next = this_node
        self.length += 1
    '''
      链表插入
    '''
    def insertlink(self, value, index):
        if index > self.length:
            # 超出范围 直接return
            return
        else:
            # 获取当前node
            this_node = Node(data=value)
            # 获取head
            current = self.head

            if index == 0:
                self.head = this_node
                this_node.next = current
                return
            while index - 1:
                current = current.next
                index -= 1
            print('insert is ',current.data)
            this_node.next = current.next
            current.next = this_node
            self.length += 1
            return
    '''
      链表删除
    '''
    def delete_index(self,index):
        if index > self.length:
            return
        else:
            if index == 0:
                self.head = self.head.next
            else:
                current = self.head
                while index - 1:
                    current = current.next
                    index -= 1
                print('delete is',current.data)
                current.next = current.next.next
                self.length -= 1
                return
    '''
      链表修改
    '''
    def update_link(self,value,index):
        if index > self.length:
            return
        else:
            this_node = Node(data=value)
            if index == 0:
                this_node.next = self.head.next
                self.head = this_node
            else:
                current = self.head
                while index - 1:
                    current = current.next
                    index -= 1
                this_node.next = current.next.next
                current.next = this_node
    def delete_final(self):
        index = self.length - 1
        current = self.head
        while index - 1:
            current = current.next
            index -= 1
        current.next = None
        self.length -= 1
        return

    def clear(self):
        """
        清空链表
        :return: None
        """
        self.head = None
        self.length = 0
        print("Clear the linked list finished.")

    def get_value(self, index):
        """
        获取链表中某个位置节点的值
        :param index: 位置索引
        :return: 该节点值, int or not
        """
        if type(index) is int:
            if index > self.length:
                # 索引值超出范围直接提示并且退出
                print("Index  is out of range.")
                return
            else:
                if index == 0:
                    return self.head.data
                else:
                    current_node = self.head
                    while index - 1:
                        current_node = current_node.pnext
                        index -= 1
                    return current_node.pnext.data
        else:
            print("Index value is not int.")
            return


def is_huan(self):
    fast = self.head
    slow = self.head
    if fast == None:
        return False
    while fast != None and fast.next != None:
        fast = fast.next.next
        slow = slow.next
        if fast == slow:
            return True
    return !(fast == None or fast.next == None)



node1 = Node('111')
node2 = Node('222')
node3 = Node('333')
node4 = Node('444')
link = linkList()
link.append_node(node1)
link.append_node(node2)
link.append_node(node3)
link.append_node(node4)

link.insertlink('666',3)
link.print_link()
link.update_link('888',3)
link.print_link()
link.delete_final()
link.print_link()