为什么这个函数删不了输入的第一组数据；其他组数据都正常删除?   
          请大师指点指点！！！！！   
Student *del_1(Student *head,long num)
{
    Student *p1,*p2;
    p2=p1=head;
    if(head==NULL)
    {   
        cout<<" list NULL;"<<endl;
        return head;
    }
    else
    {
        while(p1->next!=NULL&&p1->number!=num)
        {
            p2=p1;  p1=p1->next;
        }
        if(p1->next==NULL)
        {
            if(p1->number==num)
               p2->next=NULL;
            else
                cout<<" sorry!!!!"<<endl;
        }
        else
        {
            if(p1==head)
              head=p1->next;
            else
                p2->next=p1->next;
        }
    }
    return head;
}

什么  复制？