在第1题基础上，增加重载复数的加法和减法运算符的功能，实现两个复数的加法，一个复数与一个实数的加法；两个复数的减法，一个复数与一个实数的减法。用成员函数实现加法运算符的重载，用友元函数实现减法运算符的重载。自已设计主函数，完成程序的调试工作。

好的，下面是实现复数加减法的代码，主函数中也给出了测试样例：

#include <iostream>
using namespace std;

class Complex {
private:
    double real;
    double imag;

public:
    Complex(double r = 0.0, double i = 0.0): real(r), imag(i) {}

    Complex operator+(const Complex& c2) const;
    Complex operator+(const double& r) const;

    friend Complex operator-(const Complex& c1, const Complex& c2);
    friend Complex operator-(const Complex& c, const double& r);

    void display() const;
};

Complex Complex::operator+(const Complex& c2) const {
    Complex res;
    res.real = real + c2.real;
    res.imag = imag + c2.imag;
    return res;
}

Complex Complex::operator+(const double& r) const {
    Complex res;
    res.real = real + r;
    res.imag = imag;
    return res;
}

Complex operator-(const Complex& c1, const Complex& c2) {
    Complex res;
    res.real = c1.real - c2.real;
    res.imag = c1.imag - c2.imag;
    return res;
}

Complex operator-(const Complex& c, const double& r) {
    Complex res;
    res.real = c.real - r;
    res.imag = c.imag;
    return res;
}

void Complex::display() const {
    cout << "(" << real << ", " << imag << "i)" << endl;
}

int main() {
    Complex c1(3, 2);
    Complex c2(1, 4);
    double r = 2;

    cout << "c1 = ";
    c1.display();
    cout << "c2 = ";
    c2.display();
    cout << "r = " << r << endl;

    Complex c3 = c1 + c2;
    cout << "c1 + c2 = ";
    c3.display();

    Complex c4 = c1 + r;
    cout << "c1 + r = ";
    c4.display();

    Complex c5 = c1 - c2;
    cout << "c1 - c2 = ";
    c5.display();

    Complex c6 = c1 - r;
    cout << "c1 - r = ";
    c6.display();

    return 0;
}

输出结果为：

c1 = (3, 2i)
c2 = (1, 4i)
r = 2
c1 + c2 = (4, 6i)
c1 + r = (5, 2i)
c1 - c2 = (2, -2i)
c1 - r = (1, 2i)