HDU 3714 几何+三分法求凹曲线顶点

/****************************************************************************************************
    第一次写三分～居然是拿regional题练的。。。
****************************************************************************************************/
#include <iostream>
#include <functional>
#include <algorithm>
//#include <hash_map>		//Visual C++ lib
#include <complex>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <sstream>
#include <utility>
#include <bitset>
#include <cctype>
#include <cstdio>
#include <limits>
#include <memory>
#include <string>
#include <vector>
#include <cmath>
#include <ctime>
#include <queue>
#include <stack>
#include <list>
#include <map>
#include <set>
using namespace std;

#define LOWBIT(x) ( (x) & ( (x) ^ ( (x) - 1 ) ) )
#define CLR(x, k) memset((x), (k), sizeof(x))
#define CPY(t, s) memcpy((t), (s), sizeof(s))
#define SC(s) static_cast<int>(s)
#define LEN(s) static_cast<int>( strlen((s)) )
#define SZ(s) static_cast<int>( (s).size() )

typedef double LF;
//typedef long long LL;		//GNU C++
//typedef unsigned long long ULL;
typedef __int64 LL;		//Visual C++ 2010
typedef unsigned __int64 ULL;

typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef pair<double, double> PDD;

//typedef hash_map<int, int>::iterator HMI;
typedef map<int, int>::iterator MI;
typedef vector<int>::iterator VI;
typedef list<int>::iterator LI;
typedef set<int>::iterator SI;

const int INF_INT = 0x3f3f3f3f;
const LL INF_LL = 0x7fffffffffffffffLL;		//15f
const double oo = 10e9;
const double eps = 10e-9;
const double PI = acos(-1.0);

const int MAXN = 10004;

struct Qua
{
	LF a, b, c;
}qua[MAXN];
int test, n;

LF fun(const Qua &q, const LF &x)
{
	return q.a * x * x + q.b * x + q.c;
}
LF getmax(const LF &x)
{
	LF mx = fun(qua[0], x);
	for (int i = 1; i < n; ++i)
	{
		mx = max(mx, fun(qua[i], x));
	}
	return mx;
}
LF trisearch()
{
	LF l = 0.0, r = 1004.0, m1, m2;
	while (r - l > eps)
	{
		m1 = (2.0 * l + r) / 3.0;
		m2 = (l + 2.0 * r) / 3.0;
		if (getmax(m2) > getmax(m1))
		{
			r = m2;
		}
		else
		{
			l = m1;
		}
	}
	return (l + r) * 0.5;
}
void ace()
{
	for (cin >> test; test--; )
	{
		cin >> n;
		for (int i = 0; i < n; ++i)
		{
			cin >> qua[i].a >> qua[i].b >> qua[i].c;
		}
		printf("%.4lf\n", getmax( trisearch() ));
	}
	return ;
}
int main()
{
	ace();
	return 0;
}