请完成Complex类的定义，使得下面的主函数能正常运行。 int main( ) { Complex c1(1,2); cout<<"c1="<<c1; Complex c2(2); cout<<"c2="<<c2<<endl; Complex c3(c1); cout<<"c3="<<c3; c1=c1+c2+c3; // c1=(c1.operator+(c2)).operator+(c3); cout<<"c1=c1+c2+c3="<<c1; c2=-c3; cout<<"c2=-c3="<<c2; c3=c2-c1; cout<<"c3=c2-c1="<< c3; Complex r2=2+c2; cout<<"r2=2+c2="<<r2; Complex c4; cin>>c4; cout<<"c4="<<c4; cout<<"the module of c4 is: "<<c4.GetMagnitude()<<endl; return 0; }

#include <iostream>
#include <cmath>
using namespace std;

class Complex {
private:
    double real;
    double imag;

public:
    Complex(double r = 0, double i = 0) : real(r), imag(i) {}

    Complex operator+(const Complex& other) const {
        return Complex(real + other.real, imag + other.imag);
    }

    Complex operator-(const Complex& other) const {
        return Complex(real - other.real, imag - other.imag);
    }

    Complex operator-() const {
        return Complex(-real, -imag);
    }

    Complex operator+(double num) const {
        return Complex(real + num, imag);
    }

    Complex operator-(double num) const {
        return Complex(real - num, imag);
    }

    friend Complex operator+(double num, const Complex& c) {
        return c + num;
    }

    friend ostream& operator<<(ostream& os, const Complex& c) {
        os << c.real << "+" << c.imag << "i";
        return os;
    }

    friend istream& operator>>(istream& is, Complex& c) {
        is >> c.real >> c.imag;
        return is;
    }

    double GetMagnitude() const {
        return sqrt(real * real + imag * imag);
    }
};

int main() {
    Complex c1(1, 2);
    cout << "c1=" << c1;

    Complex c2(2);
    cout << "c2=" << c2 << endl;

    Complex c3(c1);
    cout << "c3=" << c3;

    c1 = c1 + c2 + c3;
    cout << "c1=c1+c2+c3=" << c1;

    c2 = -c3;
    cout << "c2=-c3=" << c2;

    Complex c4;
    cin >> c4;
    cout << "c4=" << c4;
    cout << "the module of c4 is: " << c4.GetMagnitude() << endl;

    return 0;
}