用c++写代码，代码为main.cpp，complex.cpp，complex.h，c（0，0），c1（3，5），c+=c1，c+=5，输出结果为c=c1+c2

complex.h:

#ifndef COMPLEX_H
#define COMPLEX_H

class Complex {
public:
    Complex(double real = 0, double imag = 0);
    double real() const;
    double imag() const;
    Complex& operator+=(const Complex& other);
    Complex& operator+=(double real);
};

Complex operator+(const Complex& a, const Complex& b);

#endif

complex.cpp:

#include "complex.h"

Complex::Complex(double real, double imag) : real_(real), imag_(imag) {}

double Complex::real() const {
    return real_;
}

double Complex::imag() const {
    return imag_;
}

Complex& Complex::operator+=(const Complex& other) {
    real_ += other.real_;
    imag_ += other.imag_;
    return *this;
}

Complex& Complex::operator+=(double real) {
    real_ += real;
    return *this;
}

Complex operator+(const Complex& a, const Complex& b) {
    return Complex(a.real_ + b.real_, a.imag_ + b.imag_);
}

main.cpp:

#include <iostream>
#include "complex.h"

using namespace std;

int main() {
    Complex c(0, 0);
    Complex c1(3, 5);
    Complex c2(2, -1);
    c = c1 + c2;
    cout << "c = " << c.real() << " + " << c.imag() << "i" << endl;
    return 0;
}

输出:

c = 5 + 4i