如何用c++面向对象来求多个圆的面积和

#include
#include

#define PI 3.14

using namespace std;

class Shape //Shape这个类里面重载了计算面积的函数
{
public:
float Shape::GetArea(float radious)//计算圆的面积
{
return float (PI*radious*radious);
}

float Shape::GetArea(float side1, float side2, float side3)//计算三角形面积
{
float average=(side1+side2+side3)/2;
return float (sqrt(average * (average-side1) * (average-side2) * (average-side3)));
}

float Shape::GetArea(float side1, float side2)//计算长方形面积
{
return float (side1 * side2);
}
};

class Triangle : public Shape
{
public:float side1, side2 ,side3;
public:
Triangle()
{
cout<<"输入三角形三边长度:"< cin>>side1>>side2>>side3;
}
};

class Circle : public Shape
{
public:float radious;
public:
Circle()
{
cout<< "输入圆的半径:"< cin>>radious;
}
};

class Rectangle : public Shape
{
public:float side1, side2;
public:
Rectangle()
{
cout<<"输入长方形的长和宽:"< cin>>side1>>side2;
}
};

int main()
{
int num;
cout<<"请选择你要计算面积的图形:"< do{
cin>>num;
switch(num){
case 1:{
Triangle* T = new Triangle;
cout<<"三角形的面积为:"<GetArea(T->side1, T->side2, T->side3)< delete T;
break;
}
case 2:{
Circle* C = new Circle;
cout<<"圆的面积为:"<GetArea(C->radious)< delete C;
break;
}
case 3:{
Rectangle* R = new Rectangle;
cout<<"长方形的面积为:"<GetArea(R->side1, R->side2)< delete R;
break;
}
default:cout<<"请在1-3之间选择:";
}
}while (num != 1|| num != 2|| num != 3);

return 0;
}