此处摘录做得较好的同学的答案

@乔南

//姓名：乔南 学号：201930100499 
#include <iostream>
using namespace std;
class Complex
{
    public:
        Complex(double x=0.0,double y=0.0):real(x),imag(y){}
        friend Complex operator+(Complex,Complex);
        friend Complex operator-(Complex,Complex);
        friend Complex operator*(Complex,Complex);
        friend bool operator==(Complex,Complex);
        friend bool operator!=(Complex,Complex);
        friend istream &operator>>(istream &,Complex&);
        friend ostream &operator<<(ostream &,Complex);
    private:
        double real;
        double imag;
};
istream &operator>>(istream &input,Complex &x)
{
    input>>x.real;
    input>>x.imag;
    return input;
}
ostream &operator<<(ostream &output,Complex x)
{
    output<<x.real;
    if(x.imag>=0)output<<"+";
    if(x.imag==-1)output<<"-";
    if(x.imag!=1&&x.imag!=-1)output<<x.imag;
    output<<"i";
    return output;
}
Complex operator+(Complex x1,Complex x2)
{
    Complex x;
    x.real=x1.real+x2.real;
    x.imag=x1.imag+x2.imag;
    return x;
}
Complex operator-(Complex x1,Complex x2)
{
    Complex x;
    x.real=x1.real-x2.real;
    x.imag=x1.imag-x2.imag;
    return x;
}
Complex operator*(Complex x1,Complex x2)
{
    Complex x;
    x.real=x1.real*x2.real-x1.imag*x2.imag;
    x.imag=x1.real*x2.imag+x1.imag*x2.real;
    return x;
}
bool operator==(Complex x1,Complex x2)
{
    return (x1.real==x2.real)&&(x1.imag==x2.imag);
}
bool operator!=(Complex x1,Complex x2)
{
    return !(x1==x2);
}
int main()
{
    Complex x1;
    Complex x2;
    cin>>x1;
    cin>>x2;
    cout<<x1+x2<<endl;
    cout<<x1-x2<<endl;
    cout<<x1*x2<<endl;
    if(x1==x2)cout<<"a==b";
    else cout<<"a!=b";
}