# coding:utf-8
class Node:
    '''
    单链表的节点
    '''
    def __init__(self,elem):
        self.elem = elem
        self.next = None

class SingleLinkList:
    '''
    单链表
    '''
    def __init__(self, node=None):
        self._head = node


    def is_empty(self):
        '''链表是否为空'''
        pass

    def length(self):
        '''返回链表的长度'''
        pass

    def travel(self):
        '''遍历整个链表 '''
        pass

    def add(self,item):
        ''' 链表头部添加元素'''
        pass

    def append(self,item):
        '''链表尾部添加元素'''
        pass

    def insert(self,pos,item):
        '''指定位置添加'''
        pass

    def remove(self,item):
        '''删除节点'''
        pass

    def search(self,item):
        '''查找节点是否存在'''
        pass