c++ class Circle

在C++中，`Circle`是一个常见的用于表示圆形的对象，它通常会被设计成一个类。下面是一个基础版的`Circle`类的例子，这个类包含了圆的基本属性（如半径`radius`）以及一些基本的操作（如计算周长和面积）：

class Circle {
public:
    // 构造函数，初始化半径
    Circle(double r) : radius(r) {}

    // 数据成员：圆的半径
    double radius;

    // 成员函数：获取圆的周长
    double getPerimeter() const {
        return 2 * M_PI * radius;
    }

    // 成员函数：获取圆的面积
    double getArea() const {
        return M_PI * pow(radius, 2);
    }

private:
    // 私有变量，保护半径不被外部直接修改
    double _radius; // 使用下划线前缀防止名称冲突

    // 计算圆周率的辅助方法（可以优化为静态全局常量）
    static double calculatePi() {
        return 3.14159; // 这里仅作为示例，实际应用中可能需要更精确的值
    }
};

相关问题

c++ 编程  Define a class Circle and derive the class Cylinder from the class Circle.  The specific requirements are as follows:  In the main function, input the radius of the circle and output the area of the corresponding circle. Then, input the height of the cylinder, output the surface area and volume of the corresponding cylinder.

下面是一个符合您要求的 C++ 代码实现：

#include<iostream>
using namespace std;

class Circle {
protected:
    double radius;
public:
    Circle(double r) : radius(r) {}
    double getArea() const {
        return 3.14 * radius * radius;
    }
};

class Cylinder : public Circle {
private:
    double height;
public:
    Cylinder(double r, double h) : Circle(r), height(h) {}
    double getSurfaceArea() const {
        return 2 * 3.14 * radius * height + 2 * Circle::getArea();
    }
    double getVolume() const {
        return Circle::getArea() * height;
    }
};

int main() {
    double r, h;
    cout << "Please input the radius of the circle: ";
    cin >> r;
    Circle c(r);
    cout << "The area of the corresponding circle is: " << c.getArea() << endl;

    cout << "Please input the height of the cylinder: ";
    cin >> h;
    Cylinder cy(r, h);
    cout << "The surface area of the corresponding cylinder is: " << cy.getSurfaceArea() << endl;
    cout << "The volume of the corresponding cylinder is: " << cy.getVolume() << endl;

    return 0;
}

在这个代码实现中，我们定义了一个圆形类 Circle，它有一个受保护的成员变量 radius 和一个公有函数 getArea()，返回圆形的面积。然后我们从 Circle 类派生出一个圆柱体类 Cylinder，它有一个私有成员变量 height 和两个公有函数 getSurfaceArea() 和 getVolume()，分别返回圆柱体的表面积和体积。在 main() 函数中，我们首先输入圆形的半径，创建一个 Circle 对象并输出其面积。然后输入圆柱体的高度，创建一个 Cylinder 对象并输出其表面积和体积。

用c++写出n Define a class Circle and derive the class Cylinder from the class Circle. n The specific requirements are as follows: l In the main function, input the radius of the circle and output the area of the corresponding circle. Then, input the height of the cylinder, output the surface area and volume of the corresponding cylinder.

Sure, here's an example implementation of the classes Circle and Cylinder in C++:

#include <iostream>
#include <cmath>

using namespace std;

class Circle {
public:
    Circle(double r) : radius(r) {}
    double area() {
        return M_PI * pow(radius, 2);
    }
protected:
    double radius;
};

class Cylinder : public Circle {
public:
    Cylinder(double r, double h) : Circle(r), height(h) {}
    double surface_area() {
        return 2 * M_PI * radius * height + 2 * Circle::area();
    }
    double volume() {
        return Circle::area() * height;
    }
private:
    double height;
};

int main() {
    double radius, height;
    cout << "Enter the radius of the circle: ";
    cin >> radius;
    Circle circle(radius);
    cout << "The area of the circle is " << circle.area() << endl;
    cout << "Enter the height of the cylinder: ";
    cin >> height;
    Cylinder cylinder(radius, height);
    cout << "The surface area of the cylinder is " << cylinder.surface_area() << endl;
    cout << "The volume of the cylinder is " << cylinder.volume() << endl;
    return 0;
}

In the `Circle` class, we define a constructor that takes a `double` argument for the radius of the circle and a method `area()` that calculates and returns the area of the circle.

In the `Cylinder` class, we define a constructor that takes two `double` arguments for the radius and height of the cylinder. We also define two methods `surface_area()` and `volume()` that calculate and return the surface area and volume of the cylinder, respectively. These methods make use of the inherited `area()` method of the `Circle` class to calculate the area of the circular base of the cylinder.

In `main()`, we prompt the user to enter the radius of the circle and the height of the cylinder, create objects of the `Circle` and `Cylinder` classes with the given values, and output the computed area, surface area, and volume using their respective methods.