UVa 10250 另两棵树

/*

* 解题思路:

* 就是求正方形给出两个对角点坐标求出另外两个

*/

#include <stdio.h>
int main( )
{
    double x1,x2,y1,y2,x,y,x3,x4,y3,y4;

    while( ~scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2 ) )
    {
         x = (x1+x2)/2;
         y = (y1+y2)/2;
        x3 = y1 - y + x;
        x4 = y - y1 + x;
        y3 = x - x1 + y;
        y4 = x1 - x + y;
        printf("%.10lf %.10lf %.10lf %.10lf\n",x3,y3,x4,y4);
    }
    return 0;
}

原文：http://blog.csdn.net/u011886588/article/details/19615209