将上述问题答案写成c++代码

抱歉，上述问题的答案不涉及具体的代码实现。但是，下面是一个简单的示例来说明如何在C++中使用虚函数和多态性：

#include <iostream>
using namespace std;

class Shape {
    protected:
        int width, height;
    public:
        Shape(int a = 0, int b = 0) {
            width = a;
            height = b;
        }
        virtual int area() {
            cout << "Parent class area :" <<endl;
            return 0;
        }
};

class Rectangle: public Shape {
    public:
        Rectangle( int a=0, int b=0):Shape(a, b) { }
        int area () { 
            cout << "Rectangle class area :" <<endl;
            return (width * height); 
        }
};

class Triangle: public Shape{
    public:
        Triangle( int a=0, int b=0):Shape(a, b) { }
        int area () { 
            cout << "Triangle class area :" <<endl;
            return (width * height / 2); 
        }
};

int main() {
    Shape *shape;
    Rectangle rec(10,7);
    Triangle  tri(10,5);

    // 存储矩形的地址
    shape = &rec;
    // 调用矩形的求面积函数 area
    shape->area();

    // 存储三角形的地址
    shape = &tri;
    // 调用三角形的求面积函数 area
    shape->area();

    return 0;
}