为什么输出结果是0（或是乱码）？）

Question

将下面代码给定输入3 3 4 3 4，为什么输出结果是0（或是乱码）？）该如何修改（对应的正确输出28.27 12.00 6.00

#include <iostream>
using namespace std;

class Shape
{
    public:
    virtual double Area() = 0;

};
class Circle :public Shape
{
public:
    double Area()
    {
     return 3.1415926 * m_R *m_R;
    }
    int m_R = 0;
};
class Rectangle : public Shape
{
public:
    double Area()
    {
        return m_W *m_L;
    }
    int m_W,m_L = 0;
};
class Triangle : public Shape
{
public:
    double Area()
    {
        return 0.5*m_B*m_H;
    }
    int m_B,m_H = 0;
};
int main()
{
    Circle circle;
    Rectangle rectangle;
    Triangle triangle;
    scanf("%d %d %d %d %d",&circle.m_R,&rectangle.m_W,&rectangle.m_L,&triangle.m_B,&triangle.m_H);   
    
    Circle *c = new Circle;
    printf("%f\n",c->Area());
    delete c;
    Rectangle *r = new Rectangle;
    printf("%f\n",r->Area());
    delete r;
    Triangle *t = new Triangle;
    printf("%f\n",t->Area());
    delete t;
    
}

Answer 1

修改如下：

#include <iostream>
using namespace std;

class Shape
{
public:
    virtual double Area() = 0;

};
class Circle :public Shape
{
public:
    double Area()
    {
        return 3.1415926 * m_R * m_R;
    }
    int m_R = 0;
};

class Rectangle : public Shape
{
public:
    double Area()
    {
        return m_W * m_L;
    }
    int m_W, m_L = 0;
};

class Triangle : public Shape
{
public:
    double Area()
    {
        return 0.5 * m_B * m_H;
    }
    int m_B, m_H = 0;
};

int main()
{
    Circle circle;
    Rectangle rectangle;
    Triangle triangle;
    scanf_s("%d %d %d %d %d", &circle.m_R, &rectangle.m_W, &rectangle.m_L, &triangle.m_B, &triangle.m_H);

    
    printf("%f\n", circle.Area());
    
    printf("%f\n", rectangle.Area());

    printf("%f\n", triangle.Area());

}

但是你这个代码太不规范了。。还有是不是对类没有理解到位。。前面已经有类实例了，后面为什么还要new一个实例