#include <iostream>
using namespace std;const float PI = 3.1416;int main()
{int iType;float radius, a, b, area;cout << "图形的类型为？(1-圆形 2-长方形 3-正方形)：";cin >> iType;switch (iType){case 1:cout << "圆的半径为：";cin >> radius;area = PI * radius*radius ;cout << "圆形的面积为：" << area << endl; break;case 2:cout << "长方形的长为：";cin >> a;cout << "长方形的宽为：";cin >> b;area = a*b;cout << "长形的面积为：" << area << endl; break;case 3:cout << "正方形的边长为：";cin >> a;area = a * a;cout << "正形的面积为：" << area << endl; break;default:break;}return 0;
}