2、（17分）
class Circle:public Shape {public:
Circle(double r){radius=r;} void set()
{ cout<<\ cin>>radius;
}
void show()
{ cout<<\
double area() {return 3.14159*radius*radius;} private: double radius;
};
class Square:public Shape {public:
Square(double a){this->a=a;} void set()
{ cout<<\ cin>>a;
}
void show()
{ cout<<\
}
double area(){return a*a;} private: double a;
};
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}
int main() { }
Circle C(5.5); C.show(); Square S(9.9); S.show();
Shape *s[]={&C,&S};
cout<<\return 0;
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