oj矩形类

#include <iostream>#include<cmath>using namespace std;class Rectangle{public:    Rectangle(double x1=0,double y1=0,double x2=0,double y2=0);    void input();    double area();    Rectangle operator+(Rectangle &);    friend ostream &operator <<(ostream &,Rectangle &r);private:    double x1,y1;double x2,y2;};Rectangle::Rectangle(double x11,double y11,double x22,double y22):x1(x11),y1(y11),x2(x22),y2(y22){}ostream &operator <<(ostream &output,Rectangle &r){  output<<r.area()<<endl;  return output;}void Rectangle::input(){  cin>>x1>>y1>>x2>>y2;}Rectangle Rectangle::operator+(Rectangle &r){    Rectangle t;    t.x1=x1+r.x1;    t.y1=y1+r.y1;    t.x2=x2+r.x2;    t.y2=y2+r.y2;    return t;}double Rectangle::area(){    return abs((x2-x1)*(y2-y1));}int main(){    Rectangle p1(1,1,6,3),p2,p3;    p2.input();    p3=p1+p2;    cout<<p3;    return 0;}

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