https://vj.xtuacm.cf/contest/view.action?cid=115#problem/K
三分简单题
#include <iostream> #include <cstdio> #include <cmath> #include <cstring> #include <algorithm> #define ll long long const int maxn=10000; using namespace std; int a[maxn+10],b[maxn+10],c[maxn+10]; double f(double n,int k) { double s=a[0]*n*n+b[0]*n+c[0]; for(int i=1;i<k;i++) s=max(s,a[i]*n*n+b[i]*n+c[i]); return s; } int main() { int t; scanf("%d",&t); while(t--) { int n; scanf("%d",&n); for(int i=0;i<n;i++) { scanf("%d%d%d",&a[i],&b[i],&c[i]); } double m,mm; double l=0,r=1000; while(fabs(r-l)>1e-12) { m=l+(r-l)/3; mm=l+2*(r-l)/3; if(f(m,n)<f(mm,n))r=mm; else l=m; } printf("%.4f\n",f(l,n)); } return 0; }