2016夏季练习——三分

来源：HDU 3714

三分还是蛮简单的，直接上代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
const double eps = 1e-9;
const int MAXN = 10010;
const double IDOUBLE=(~0U>>1);
int n;
int a[MAXN];
int b[MAXN];
int c[MAXN];
double fun(double x,int pos){
	return x*x*a[pos]*1.0+x*b[pos]*1.0+c[pos]*1.0;
}
double calc(double x){
	double ans=-IDOUBLE;
	for(int i=0;i<n;i++){
		ans=max(ans,fun(x,i));
	}
	return ans;
}
bool judge(double mid,double midmid){
	return calc(mid)<calc(midmid);
}
int main(){
	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 left=0;
		double right=1000;
		double mid=(left+right)/2;
		double midmid=(right+mid)/2;
		while(abs(mid-midmid)>eps){
			mid=(left+right)/2;
			midmid=(right+mid)/2;
			if(judge(mid,midmid)){
				right=midmid;
			}
			else{
				left=mid;
			}
		}
		printf("%.4f\n",calc(mid));
	}
	return 0;
}