代码：

#include <iostream.h>

struct POINT
{
 double x;
 double y;
};

struct RECTANGLE
{
 POINT ptlefttop;
 POINT ptrightbottom;
};

double Area(RECTANGLE rec)
{
 double recarea;
 recarea=(rec.ptlefttop.y-rec.ptrightbottom.y)*(rec.ptrightbottom.x-rec.ptlefttop.x);
 return recarea;
}

void main()
{
 RECTANGLE rec;

 cout<<"请输入长方形左上角顶点坐标："<<endl;
 cout<<"x=";
 cin>>rec.ptlefttop.x;
 cout<<"y=";
 cin>>rec.ptlefttop.y;
 cout<<"请输入长方形右下角顶点坐标："<<endl;
 cout<<"x=";
 cin>>rec.ptrightbottom.x;
 cout<<"y=";
 cin>>rec.ptrightbottom.y;
 cout<<"长方形面积："<<Area(rec)<<endl;

}

http://s11/middle/63a7c6abnbbcb7ad7c32a&690