敲代码的第十九天：利用继承和多态求正方体，圆柱体，球体的面积和体积（c++）

#include<iostream>
using namespace std;

class basic {
public:
    virtual double superficial_area() = 0;
    virtual double volume() = 0;

    ~basic()
    {}
};

class cube :public basic
{
private:
    double length;
public:
    cube(double a) :length(a)
    {}
    double superficial_area()
    {
        return(6 * length * length);
    }
    double volume()
    {
        return(length * length * length);
    }
    ~cube()
    {}
};

class cylinder :public basic
{
private:
    double radius;
    double high;
public:
    cylinder(double a, double b) :radius(a), high(b)
    {}
    double superficial_area()
    {
        return ((2 * 3.1415 * radius * radius) + (2 * 3.1415 * radius * high));