[黄金分割比] 黄金分割法求单峰函数最值

论文：杨思雨--美，无处不在——浅谈“黄金分割”和信息学的联系

#include<cstdio>#include<cstdlib>#include<algorithm>#include<cmath>using namespace std;const double eps=1e-4;const double phi=(sqrt(5.0)-1)/2;double A,B,C;double L,R;int cnt=0;inline double F(double x){  cnt++;  return A*x*x+B*x+C;}int main(){  freopen("t.in","r",stdin);  freopen("t.out","w",stdout);  scanf("%lf%lf%lf%lf",&A,&B,&C,&R);  L=0; int left=0,right=0;  double x1,x2,f1,f2;   while (R-L>eps){    if (!left)      x1=R-(R-L)*phi,f1=F(x1);    if (!right)      x2=L+(R-L)*phi,f2=F(x2);    if (f1<f2){      L=x1; x1=x2; f1=f2; left=1; right=0;    }else{      R=x2; x2=x1; f2=f1; right=1; left=0;    }  }  printf("%.3lf\n",L);  freopen("c.out","w",stdout);  printf("%d\n",cnt);  return 0;}