定义一个复数类complex ，重载运算符"<<"实现复数形式的输出，重载运算符“+”使之用于复数的加法运算，两个复数之和，复数与整数之和

下面是一个示例代码：

#include <iostream>
using namespace std;

class complex {
private:
    double real, imag;  // 复数的实部和虚部
public:
    complex(double r = 0.0, double i = 0.0) : real(r), imag(i) {}
    friend ostream& operator<<(ostream& os, const complex& c);
    friend complex operator+(const complex& c1, const complex& c2);
    friend complex operator+(const complex& c, const int& i);
};

ostream& operator<<(ostream& os, const complex& c) {
    os << c.real;
    if (c.imag > 0) os << "+";
    if (c.imag != 0) os << c.imag << "i";
    return os;
}

complex operator+(const complex& c1, const complex& c2) {
    return complex(c1.real + c2.real, c1.imag + c2.imag);
}

complex operator+(const complex& c, const int& i) {
    return complex(c.real + i, c.imag);
}

int main() {
    complex c1(1.0, 2.0), c2(3.0, -4.0), c3;
    c3 = c1 + c2;
    cout << c1 << " + " << c2 << " = " << c3 << endl;
    c3 = c1 + 5;
    cout << c1 << " + " << 5 << " = " << c3 << endl;
    return 0;
}

输出结果为：

1+2i + 3-4i = 4-2i
1+2i + 5 = 6+2i

这里使用了友元函数来重载输出运算符和加法运算符。在输出时，如果虚部为负数，则会自动输出符号。在加法运算时，复数对象与整数相加时，整数被视为虚部为0的复数。