UVa1476 Error Curves

 1 /*by SilverN*/
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cmath>
 7 using namespace std;
 8 const int mxn=10020;
 9 int a[mxn],b[mxn],c[mxn];
10 int n;
11 double f(double x){
12     double ans=a[1]*x*x+b[1]*x+c[1];
13     for(int i=2;i<=n;i++)
14         ans=max(ans,a[i]*x*x+b[i]*x+c[i]);
15     return ans;
16 }
17 int main(){
18     int T;
19     scanf("%d",&T);
20     int i,j;
21     while(T--){
22         scanf("%d",&n);
23         for(i=1;i<=n;i++){
24             scanf("%d%d%d",&a[i],&b[i],&c[i]);
25 //            a[i]=read();b[i]=read();c[i]=read();
26 //            printf("%d %d %d\n",a[i],b[i],c[i]);
27         }
28         double l=0,r=1000;
29         for(i=1;i<=450;i++){
30             double mid1=(l*2+r)/3;
31             double mid2=(l+r*2)/3;
32             if(f(mid1)<f(mid2))r=mid2;
33             else l=mid1;
34         }
35         printf("%.4f\n",f(l));
36     }
37     return 0;
38 }