HDU 5144 三分

开始推导用公式求了好久（真的蠢），发现精度有点不够。

其实这种凸线上求点类的应该上三分法的，当作入门吧...

/** @Date    : 2017-09-23 21:15:57
  * @FileName: HDU 5144 三分 无聊物理题.cpp
  * @Platform: Windows
  * @Author  : Lweleth ([e-mail])
  * @Link    : https://github.com/
  * @Version : $Id$
  */
#include <bits/stdc++.h>
#define LL long long
#define PII pair<int ,int>
#define MP(x, y) make_pair((x),(y))
#define fi first
#define se second
#define PB(x) push_back((x))
#define MMG(x) memset((x), -1,sizeof(x))
#define MMF(x) memset((x),0,sizeof(x))
#define MMI(x) memset((x), INF, sizeof(x))
using namespace std;

const int INF = 0x3f3f3f3f;
const int N = 1e5+20;
const double eps = 1e-8;
const double Pi = acos(-1.0);
const double g = 9.80;

double check(double agl, double v0, double h)
{
	double va = v0 * sin(agl);
	double vb = v0 * cos(agl);
	double c = 2 * g * h;
	double t1 = va / g;
	double t2 = sqrt(c + va * va) / g;
	double x = (t1 + t2) * vb;
	return x;
}

int main()
{
	int T;
	cin >> T;
	while(T--)
	{
		double h, v;
		scanf("%lf%lf", &h, &v);
		double l = 0, r = Pi / 2.0;
		while(r - l > eps)
		{
			double lmid = l + (r - l) / 3.00;
			double rmid = r - (r - l) / 3.00;
			if(check(lmid,v,h) > check(rmid,v,h))
				r = rmid;
			else l = lmid;
		}
		printf("%.2lf\n", check(l,v,h));
	}
    return 0;
}