有如下程序: #include <iostream> using namespaee std; class ONE{ public: virtual void f( ){cout<<"1";} }; class TWO:public ONE{ public: TWO( )1 cout<<"2";} {; class THREE:public TWO{ public: virtual void f( )}TWO::f( );cout<<"3";} }; int main( ){ ONE aa,*P; TWO bb; THREE cc; P=&cc; p->f( ); return 0; } 程序的输出结果是______。