python数据结构-单链表

class Node():
    def __init__(self,item):
        self.item=item
        self.next=None
    
class SingleList():
    def __init__(self):
        self.__head=None
    def is_empty(self):
        return self.__head==None
    def length(self):
        if self.__head==None:
            return 0
        cur=self.__head
        count=0
        while cur:
            count+=1
            cur=cur.next
        return count
    #尾插法
    def append(self,item):
        node=Node(item)
        if self.__head==None:
            self.__head=node
        else:
            cur=self.__head
            while cur.next:
                cur=cur.next
        cur.next=node
    #头插法
    def add(self,item):
        node=Node(item)
        node.next=self.__head
        self.__head=node
    #遍历
    def travel(self):
        cur=self.__head
        if self.__head==None:
            return        
        else:
            while cur:
                print(cur.item,end='')
                cur=cur.next
    #插入
    def insert(self,item,pos):
        node=Node(item)
        count=0
        cur=self.__head
        if pos<=0:
            self.add(item)
        elif pos>self.length()-1:
            self.append(item)
        else:
            while count<pos-1:
                count+=1
                cur=cur.next
            node.next=cur.next
            cur.next=node
    #查询
    def search(self,item):
        if self.__head==None:
            return
        cur=self.__head
        while cur:
            if cur.item!=item:
                cur=cur.next
            else:
                return True
        return False
    #移除
    def remove(self,item):
        if self.__head==None:
            return
        cur=self.__head
        pre=None
        while cur.item==item:
            if cur==self.__head:
                self.__head=cur.next
            else:
                pre.next=cur.next
            break
        pre=cur
        cur=cur.next
#测试
if __name__=='__main__':
    singlelist=SingleList()
    singlelist.add(2)
    singlelist.add(1)
    singlelist.append(3)
    singlelist.append(4)
    singlelist.append(5)
    singlelist.travel()
    print()
    singlelist.insert(6,3)
    singlelist.travel()
    print()
    print(singlelist.search(5))
    singlelist.remove(1)
    singlelist.travel()