UVA 10250 - The Other Two Trees（几何）

        在纸上画了下，用全等三角形定则，找了下规律。

 

#include <stdio.h>#include <math.h>double compute(double x1, double y1, double x2, double y2) {    return (x1+x2+y1-y2)/2;}int main() {    double x[4], y[4];    while (scanf("%lf%lf%lf%lf", &x[0], &y[0], &x[1], &y[1]) != EOF) {        if (fabs(x[0]-x[1])<1e-9 && fabs(y[0]-y[1])<1e-9) {            printf("Impossible.\n");            continue;        }        x[2] = compute(x[0], y[0], x[1], y[1]);        x[3] = compute(x[1], y[1], x[0], y[0]);        y[3] = compute(y[0], x[0], y[1], x[1]);        y[2] = compute(y[1], x[1], y[0], x[0]);        printf("%.10lf %.10lf %.10lf %.10lf\n", x[2], y[2], x[3], y[3]);    }    return 0;}