nyoj 1029/hdu 3714 Error Curves 三分
题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=3714
懂了三分思想和F(x)函数的单调性质,这题也就是水题了
#include "stdio.h" //最后得到的F(x)函数要么是单调的,要么是先减后增的,有了这个性质,就可以三分了~ #include "string.h" #define N 10005 #define eps 1e-9 #define INF 0x3fffffff struct node { int a; int b; int c; }q[N]; int n; double S(double x) { double sx; double maxt = -INF; for(int i=0; i<n; ++i) { sx = q[i].a*x*x+q[i].b*x+q[i].c; if(sx>maxt) maxt = sx; } return maxt; } int main() { int i,T; double ans_mid,ans_mid_mid; double left,right,mid,mid_mid; scanf("%d",&T); while(T--) { scanf("%d",&n); for(i=0; i<n; ++i) scanf("%d %d %d",&q[i].a,&q[i].b,&q[i].c); left = 0; right = 1000; while(right-left>eps) { mid = (right+left)/2; ans_mid = S(mid); mid_mid = (mid+right)/2; ans_mid_mid = S(mid_mid); if(ans_mid>ans_mid_mid) left = mid; else right= mid_mid; } printf("%.4lf\n",S(right)); } }