下列程序的输出结果是______。 #include<iostream> using namespace std; class base public: int n; base(int x) n=x; virtual void set(int m) n=m;cout << n <<’ ’; ; class deriveA:public base public: deriveA(int x):base(x) void set(int m) n += m;cout << n <<’ ’; ; class deriveB:public base public: deriveB(int x):base(x) void set(int m) n +=m; cout << n<<’ ’; ; int main() deriveA d1(1); deriveB.d2(3); base *pbase; pbase=&d1; pbase->set(1); pbase= &d2; pbase->set(2); return 0;