链接：Miku

三分法的模板，和是一个东西

对于修正量的精度要求极高

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
double a[100001],b[100001],c[100001];
int t;
int n;
double l,r;
double xiu=1e-9;
double ch(double x){
    double ans=-0x7fff77ff;
    double l=0;
    for(int i=1;i<=n;++i){
        ans=max(ans,(double)x*x*a[i]+x*b[i]+c[i]);
    }
    return ans;
}
int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        for(int i=1;i<=n;++i){
            scanf("%lf%lf%lf",&a[i],&b[i],&c[i]);
        }   
        l=0.0;
        r=1000.0;
        while(l+xiu<r){
        //  cout<<l<<" "<<r<<endl;
            double lm=l+(r-l)*0.3;
            double rm=l+(r-l)*0.7;
            if(ch(lm)<ch(rm)){
                r=rm;
            }else
            l=lm;
        }
        printf("%.4lfn",ch(l));
    } 
    return 0;
}