问题详情

下列程序的输出结果是______。
include＜iostream.h＞
class base
{
int x,y;
public:
base(int i,int j){x=i;y=j;}
virtual int add(){return x+y;}
};
class three:public base
{
int z;
public:
three(int i,int j,int k):base(i,j){z=k;)
int add(){return(base::add()+z);}
};
void main()
{
three*q=new three(10,20,30);
cout＜＜q-＞add()＜＜endl;
}请帮忙给出正确答案和分析，谢谢！