6-3 重载+-运算符 (10分)
请根据程序的输出结果，重载类A的+和-运算符。
类和函数接口定义：
class A {
public:
A(int x = 0, int y = 0) : x(x), y(y) {}
void show() const;
A operator+(A& a); //重载+运算符
A operator-(A& a); //重载-运算符
private:
int x, y;
};
裁判测试程序样例：
#include <iostream>
using namespace std;
class A {
public:
A(int x = 0, int y = 0) : x(x), y(y) {}
void show() const;
A operator+(A& a);
A operator-(A& a);
private:
int x, y;
};
void A::show() const {
cout << "(x,y) = " << "(" << x << "," << y << ")" << endl;
}
/* 请在这里填写答案 */
int main() {
A a1(1, 2);
A a2(4, 5);
A a;
cout << "a1:"; a1.show();
cout << "a2:"; a2.show();
a = a1 + a2;
cout << "a:"; a.show();
a = a1 - a2;
cout << "a:"; a.show();
return 0;
}
输入样例：
本题无输入。
输出样例：
a1:(x,y) = (1,2)
a2:(x,y) = (4,5)
a:(x,y) = (5,7)
a:(x,y) = (-3,-3)
A A::operator+(A& a)
{
return A(x+a.x,y+a.y);
}
A A::operator-(A& a)
{
return A(x-a.x,y-a.y);
}//没什么好说的，很简单
