灯泡

题目描述

思路

代码

#include <cstdio>

int n;
double H, h, D, l, r, midl, midr, ans, ansl, ansr;
double calc(double x) {
	return x + D * (h - x) / (H - x);
}
int main() {
	scanf("%d", &n);
	while (n--) {
		scanf("%lf %lf %lf", &H, &h, &D);
		l = 0, r = h;
		while (r - l > 1e-6) {
			midl = l + (r - l) / 3.0;
			midr = r - (r - l) / 3.0;
			ansl = calc(midl), ansr = calc(midr);
			if (ansl < ansr) ans = ansr, l = midl;
			else ans = ansl, r = midr;
		}
		printf("%.3lf\n", ans);
	}
	
	return 0;
}