PTA 复数类的运算

根据以下代码段完善 ?? 处内容及程序内容，以实现规定的输出。

class Complex
{
    public:
        Complex(double r=0, double i=0):real(r), imag(i){    }
        Complex operator+( ?? ) const;//重载双目运算符'+'
        Complex operator-=( ?? ); //重载双目运算符'-='
        friend Complex operator-( ?? ) const;//重载双目运算符'-'
        void Display() const;
    private:
        double real;
        double imag;
};

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

int main()
{
    double r, m;
    cin >> r >> m;
    Complex c1(r, m);
    cin >> r >> m;
    Complex c2(r, m);
    Complex c3 = c1+c2;
    c3.Display();
    c3 = c1-c2;
    c3.Display();
    c3 -= c1;
    c3.Display();
    return 0;
}

输入格式:

输入有两行，分别为两个复数的实部与虚部。

输出格式:

按样例格式输出结果。

输入样例:

在这里给出一组输入。例如：

4 2
3 -5
结尾无空行

输出样例:

在这里给出相应的输出。例如：

(7, -3)
(1, 7)
(-3, 5)
结尾无空行

代码：

#include <iostream>
using namespace std;
class Complex
{
	public:
		Complex(double r=0, double i=0):real(r), imag(i){	}
		Complex operator+(Complex c) const;//重载双目运算符'+'
		Complex operator-=(Complex c); //重载双目运算符'-='
		friend Complex operator-(Complex c1,Complex c2) ;//重载双目运算符'-'
		void Display() const;
	private:
		double real;
		double imag;
};
Complex Complex::operator+ (Complex c)const{
c.imag=c.imag+this->imag;
c.real=c.real+this->real;
return c;
}
Complex Complex::operator-=(Complex c){
this->imag=this->imag-c.imag;
this->real=this->real-c.real;
return *this;

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

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

int main()
{
	double r, m;
	cin >> r >> m;
	Complex c1(r, m);
	cin >> r >> m;
	Complex c2(r, m);
	Complex c3 = c1+c2;
	c3.Display();
	c3 = c1-c2;
	c3.Display();
	c3 -= c1;
	c3.Display();
	return 0;
}

提交结果：