LA 5009 3点

#include <cstdio>
#include <algorithm>
using namespace std;
const int maxn = 10000 + 10;
int n, a[maxn], b[maxn], c[maxn];
double F(double x)
{
	double ans = a[0] * x * x + b[0] * x + c[0];
	for (int i = 1; i < n; i++)
		ans = max(ans, a[i] * x * x + b[i] * x + c[i]);
	return ans;
}
int main(int argc, char const *argv[])
{
	int T;
	scanf("%d", &T);
	while (T--)
	{
		scanf("%d", &n);
		for (int i = 0; i < n; i++)
			scanf("%d%d%d", a + i, b + i, c + i);
		double L = 0.0, R = 1000.0;
		for (int i = 0; i < 100; i++)
		{
			double m1 = L + (R - L) / 3;
			double m2 = R - (R - L) / 3;
			if (F(m1) < F(m2)) R = m2;
			else L = m1;
		}
		printf("%.4lf
", F(L));
	}
	return 0;
}

単一ピーク関数は3点を使用して値を求めます