定义一个Cube类

        计算表面积和体积，并判断长方体是否相等（分别用全局函数和成员函数来实现）。

参考代码：

#include <iostream>

using namespace std;
class Cube {
private:
    double m_l;
    double m_w;
    double m_h;
public:
    //设置长宽高
    void setL(double l) {
        m_l = l;
    }
    void setW(double w) {
        m_w = w;
    }
    void setH(double h) {
        m_h = h;
    }
    //获得长宽高
    double getL() {
        return m_l;
    }
    double getW() {
        return m_w;
    }
    double getH() {
        return m_h;
    }
    //计算面积
    double getA() {
        return (m_l * m_w + m_l * m_h + m_w * m_h) * 2;
    }
    //计算体积
    double getV() {
        return m_l * m_w * m_h;
    }
    //成员函数判断长方体是否相等
    //长方体的长宽高顺序不一，需要重复判断
    bool compareCube2(Cube &ob) {
        if((m_l = ob.m_l) && (m_w == ob.m_w) && (m_h == ob.m_h)) {
            return true;
        } else if((m_l = ob.m_l) && (m_w == ob.m_h) && (m_h == ob.m_w)) {
            return true;
        } else if((m_l = ob.m_w) && (m_w == ob.m_l) && (m_h == ob.m_h)) {
            return true;
        } else if((m_l = ob.m_w) && (m_w == ob.m_h) && (m_h == ob.m_l)) {
            return true;
        } else if((m_l = ob.m_h) && (m_w == ob.m_w) && (m_h == ob.m_l)) {
            return true;
        } else if((m_l = ob.m_h) && (m_w == ob.m_l) && (m_h == ob.m_w)) {
            return true;
        } else {
            return false;
        }
    }

};
//全局函数判断长方体是否相等
//长方体的长宽高顺序不一，需要重复判断
bool compareCube(Cube &cube1, Cube &cube2) {
    if((cube1.getL() == cube2.getL()) && (cube1.getW() == cube2.getW()) \
            && (cube1.getH() == cube2.getH())) {
        return true;
    }
    if((cube1.getL() == cube2.getL()) && (cube1.getW() == cube2.getH()) \
            && (cube1.getH() == cube2.getW())) {
        return true;
    }
    if((cube1.getL() == cube2.getW()) && (cube1.getW() == cube2.getL()) \
            && (cube1.getH() == cube2.getH())) {
        return true;
    }
    if((cube1.getL() == cube2.getW()) && (cube1.getW() == cube2.getH()) \
            && (cube1.getH() == cube2.getL())) {
        return true;
    }
    if((cube1.getL() == cube2.getH()) && (cube1.getW() == cube2.getL()) \
            && (cube1.getH() == cube2.getW())) {
        return true;
    }
    if((cube1.getL() == cube2.getH()) && (cube1.getW() == cube2.getW()) \
            && (cube1.getH() == cube2.getL())) {
        return true;
    }
    return false;
}

void test() {
    //长方体1
    Cube cube1;
    cube1.setL(2);
    cube1.setW(1);
    cube1.setH(3);
    cout << "计算长方体1面积:" << cube1.getA() << endl;
    cout << "计算长方体1体积:" << cube1.getV() << endl;
    cout << "----------------" << endl;
    //长方体2
    Cube cube2;
    cube2.setL(1);
    cube2.setW(3);
    cube2.setH(2);
    cout << "计算长方体2面积:" << cube2.getA() << endl;
    cout << "计算长方体2体积:" << cube2.getV() << endl;
    cout << "----------------" << endl;
    //长方体3
    Cube cube3;
    cube3.setL(1);
    cube3.setW(2);
    cube3.setH(5);
    cout << "计算长方体3面积:" << cube3.getA() << endl;
    cout << "计算长方体3体积:" << cube3.getV() << endl;
    cout << "----------------" << endl;
    //全局函数
    cout << "长方体1 长方体2" << endl;
    if(compareCube(cube1, cube2) == true) {
        cout << "两个长方体相等" << endl;
    } else {
        cout << "两个长方体不相等" << endl;
    }
    cout << "----------------" << endl;
    //成员函数
    cout << "长方体1 长方体3" << endl;
    if(cube3.compareCube2(cube1) == true) {
        cout << "两个长方体相等" << endl;
    } else {
        cout << "两个长方体不相等" << endl;
    }
}
int main() {
    test();
    return 0;
}

运行结果：