c++-面向对象类的示例-求周长面积，判断体积相等-文件操作和一般操作

面向对象编程示例：求周长和面积

#define _crt_secure_no_warnings
#include <iostream>


using namespace std;

//圆的周长
double getcirclegirth(double r)
{
    return 2 * 3.14*r;
}

//源的面积
double getcirclearea(double r)
{
    return 3.14*r*r;
}

//用面向对象实现

//圆类
class circle
{
public:
    void setr(double r)
    {
        m_r = r;
    }

    double getr()
    {
        return m_r;
    }

    double getgirth()
    {
        return 2 * 3.14 *m_r;
    }

    double getarea()
    {
        return m_r*m_r*3.14;
    }

private:
    double m_r; //圆的私有成员 半径
};

class circle2
{
public:

    void setr(double r)
    {
        m_r = r;
    }

    double getr()
    {
        return m_r;
    }

    double getarea()
    {
        m_area = m_r*m_r*3.14;
        return m_area;
    }

    double getgirth()
    {
        m_girth = m_r * 2 * 3.14;
        return m_girth;
    }

private:
    double m_r;
    double m_girth; //周长
    double m_area;//面积
};


int main(void)
{
    double r = 10; //圆的半径

    double g = 0;
    double a = 0;

    g = getcirclegirth(r);
    a = getcirclearea(r);
    cout << "圆的半径是" << r << endl;
    cout << "圆的周长是" << g << endl;
    cout << "圆的面积是" << a << endl;

    cout << "------" << endl;

    circle c;

    c.setr(10);

    cout << "圆的半径是" << c.getr() << endl;
    cout << "圆的周长是" << c.getgirth() << endl;
    cout << "圆的面积是" << c.getarea() << endl;

    cout << "------------" << endl;

    circle2 c2;

    c2.setr(10);


    cout << "圆的半径是" << c2.getr() << endl;
    cout << "圆的周长是" << c2.getgirth() << endl;
    cout << "圆的面积是" << c2.getarea() << endl;

    return 0;
}

上面那个多文件形式（模块化？(^▽^)）

main.cpp

#define _crt_secure_no_warnings
#include <iostream>

#include "circle.h"

using namespace std;

int main(void)
{
    circle c;
    c.setr(10);

    cout << "ãæ»ý" << c.getarea() << endl;


    return 0;
}

circle.h

#pragma once

#if 0
#ifndef __circle_h_
#define __circle_h_


#endif
#endif

class circle
{
public:
    //éèöã°ë¾¶£º
    void setr(double r);
    //µãµ½°ë¾¶
    double getr();

    double getarea();

    double getgirth();

private:
    double m_r;
    double m_area;
    double m_girth;
};

circle.cpp

#include "circle.h"

void circle::setr(double r)
{
    m_r = r;
}


double circle::getr()
{
    return m_r;
}

double circle::getarea()
{
    m_area = m_r *m_r *3.14;

    return m_area;
}

double circle::getgirth()
{
    m_girth = m_r * 2 * 3.14;

    return m_girth;
}

示例：判断立方体相等

#define _crt_secure_no_warnings
#include <iostream>


using namespace std;

//立方体类
class cube
{
public:
    void setabc(int a, int b, int c)
    {
        m_a = a;
        m_b = b;
        m_c = c;
    }

    int getarea()
    {
        return (m_a*m_b) * 2 + (m_a*m_c) * 2 + (m_b*m_c) * 2;
    }

    int getvolume()
    {
        return (m_a*m_b*m_c);
    }

    int geta()
    {
        return m_a;
    }

    int getb()
    {
        return m_b;
    }

    int getc()
    {
        return m_c;
    }

    //同类之间无私处
    bool judgecube(cube &another)
    {
        if (m_a == another.m_a &&
            m_b == another.getb() &&
            m_c == another.getc()) {
            return true;
        }
        else {
            return false;
        }
    }
private:
    int m_a;
    int m_b;
    int m_c;
};

//全局函数
bool judgecube(cube &c1, cube &c2)
{
    if (c1.geta() == c2.geta() &&
        c1.getb() == c2.getb() &&
        c1.getc() == c2.getc()) {
        return true;
    }
    else {
        return false;
    }
}

int main(void)
{
    cube c1;
    c1.setabc(10, 20, 30);

    cube c2;
    c2.setabc(10, 20, 30);

    cout << "c1 的体积是" << c1.getvolume() << endl;
    cout << "c1 的面积是" << c1.getarea() << endl;

    if (judgecube(c1, c2) == true) {
        cout << "相等" << endl;
    }
    else {
        cout << "不相等" << endl;
    }
    cout << " ------ " << endl;

    if (c1.judgecube(c2) == true) {
        cout << "相等" << endl;
    }
    else {
        cout << "不相等" << endl;
    }


    return 0;
}

示例：求点是否在圆内

#define _crt_secure_no_warnings
#include <iostream>


using namespace std;

//点类
class point
{
public:
    void setxy(int x, int y)
    {
        m_x = x;
        m_y = y;
    }

    int getx()
    {
        return m_x;
    }

    int gety()
    {
        return m_y;
    }
private:
    int m_x;
    int m_y;
};

//圆类
class circle
{
public:
    void setxy(int x, int y)
    {
        x0 = x;
        y0 = y;
    }

    void setr(int r)
    {
        m_r = r;
    }

    //提供一个判断点是否在圆内
    //true 在内部
    //false 在外部
    bool judgepoint(point &p)
    {
        int dd;

        dd = (p.getx() - x0)*(p.getx() - x0) + (p.gety() - y0)*(p.gety() - y0);

        if (dd > m_r*m_r) {
            return false;
        }
        else {
            return true;
        }
    }


private:
    int x0;
    int y0;
    int m_r;
};

int main(void)
{
    circle c;
    c.setxy(2, 2);
    c.setr(4);

    point p;
    p.setxy(8, 8);

    if (c.judgepoint(p) == true) {
        cout << "圆的内部" << endl;
    }
    else {
        cout << "圆的外部" << endl;
    }



    return 0;
}

上面代码的文件形式

main.cpp

#define _crt_secure_no_warnings
#include <iostream>
#include "circle.h"
#include "point.h"

using namespace std;

int main(void)
{
    circle c;
    c.setr(4);
    c.setxy(2, 2);

    point p;
    p.setxy(8, 8);

    if (c.judgepoint(p) == true) {
        cout << "nei" << endl;
    }
    else {
        cout << "wai" << endl;
    }
    
    return 0;
}

circle.h

#pragma once
#include "point.h"

class circle
{
public:
    void setxy(int x, int y);

    void setr(int r);

    //提供一个判断点是否在圆内
    //true 在内部
    //false 在外部
    bool judgepoint(point &p);

private:
    int x0;
    int y0;
    int m_r;
};

circle.cpp

#include "circle.h"

void circle::setxy(int x, int y)
{
    x0 = x;
    y0 = y;
}

void circle::setr(int r)
{
    m_r = r;
}

//提供一个判断点是否在圆内
//true 在内部
//false 在外部
bool circle::judgepoint(point &p)
{
    int dd;

    dd = (p.getx() - x0)*(p.getx() - x0) + (p.gety() - y0)*(p.gety() - y0);

    if (dd > m_r*m_r) {
        return false;
    }
    else {
        return true;
    }
}

point.h

#pragma once


class point
{
public:
    void setxy(int x, int y);

    int getx();

    int gety();
private:
    int m_x;
    int m_y;
};

point.cpp

#include "point.h"


void point::setxy(int x, int y)
{
    m_x = x;
    m_y = y;
}

int  point::getx()
{
    return m_x;
}

int point::gety()
{
    return m_y;
}