[HDOJ3714]Error Curves（三分）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=3714

题意：求n个二次函数在[0,1000]的最小值。

三分枚举。

 #include <bits/stdc++.h>
 using namespace std;

 const int maxn = ;
 const double eps = 1e-;
 double a[maxn], b[maxn], c[maxn];
 int n;

 double f(double x) {
   double ret = -;
   for(int i = ; i <= n; i++) {
     double y = a[i]*x*x+b[i]*x+c[i];
     ret = max(ret, y);
   }
   return ret;
 }

 double ts() {
   double lo = , hi = 1000.0;
   double ret1, ret2;
   while(hi - lo >= eps) {
     double mid = (lo + hi) / 2.0;
     double mimid = (mid + hi) / 2.0;
     ret1 = f(mid);
     ret2 = f(mimid);
     if(ret1 > ret2) lo = mid;
     else hi = mimid;
   }
   return ret1;
 }

 int main() {
   //freopen("in", "r", stdin);
   int T;
   scanf("%d", &T);
   while(T--) {
     scanf("%d", &n);
     for(int i = ; i <= n; i++) {
       scanf("%lf %lf %lf", &a[i], &b[i], &c[i]);
     }
     printf("%.4lf\n", ts());
   }
   return ;
 }