UVALive 5009 Error Curves 三分

//#pragma comment(linker, "/STACK:1024000000,1024000000")

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<algorithm>

#include<iostream>

#include<sstream>

#include<cmath>

#include<climits>

#include<string>

#include<map>

#include<queue>

#include<vector>

#include<stack>

#include<set>

using namespace std;

typedef long long ll;

typedef unsigned long long ull;

typedef pair<int,int> pii;

#define pb(a) push(a)

#define INF 0x1f1f1f1f

#define lson idx<<1,l,mid

#define rson idx<<1|1,mid+1,r

#define PI  3.1415926535898

template<class T> T min(const T& a,const T& b,const T& c) {

    return min(min(a,b),min(a,c));

}

template<class T> T max(const T& a,const T& b,const T& c) {

    return max(max(a,b),max(a,c));

}

void debug() {

#ifdef ONLINE_JUDGE

#else

freopen("in.txt","r",stdin);

    //freopen("d:\\out1.txt","w",stdout);

#endif

}

int getch() {

    int ch;

    while((ch=getchar())!=EOF) {

        if(ch!=‘ ‘&&ch!=‘\n‘)return ch;

    }

    return EOF;

}
const int maxn=10005;

int a[maxn],b[maxn],c[maxn];

double f(int i,double x)

{

    return a[i]*x*x+b[i]*x+c[i];

}

int n;

double  check(double x)

{

    double maxx=f(1,x);

    for(int i=2;i<=n;i++)

        maxx=max(maxx,f(i,x));

    return maxx;

}

int main()

{

    int t;

    scanf("%d",&t);

    for(int ca=1;ca<=t;ca++)

    {

        //int n;

        scanf("%d",&n);

        double maxx=-(1<<29);

        for(int i=1;i<=n;i++)

        {

            scanf("%d%d%d",&a[i],&b[i],&c[i]);

        }

        double l=0,r=1005;

        const double eps=1e-9;

        while(r-l>eps)

        {

            double ll=(2*l+r)/3;

            double rr=(l+2*r)/3;

            if(check(ll)<check(rr))

                r=rr;

            else l=ll;

        }

        printf("%.4lf\n",check(l));

    }

    return 0;

}

UVALive 5009 Error Curves 三分