BZOJ1502: [NOI2005]月下柠檬树

Simpson法相当好用啊！神奇的骗分算法！

 /**************************************************************
     Problem: 1502
     User: zhuohan123
     Language: C++
     Result: Accepted
     Time:228 ms
     Memory:1312 kb
 ****************************************************************/

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 using namespace std;
 const double eps=1e-,pi=3.141592653589793238;
 int n;
 struct point
 {
     double x,y;
     point(){}
     point(double X,double Y){x=X,y=Y;}
 };
 struct line
 {
     point s,e;
     line(){}
     line(point S,point E){s=S,e=E;}
     double y(double x){return (e.y*s.x-e.x*s.y-e.y*x+s.y*x)/(s.x-e.x);}
 }l[];int lnum;
 struct circle{double x,r;}c[];
 double h[];
 double f(double x)
 {
     double s=;
     for(int i=;i<n;i++)
     {
         if(abs(x-c[i].x)+eps<c[i].r)s=max(s,sqrt(c[i].r*c[i].r-(x-c[i].x)*(x-c[i].x)));
         if(l[i].s.x<x+eps&&l[i].e.x>x-eps)s=max(s,l[i].y(x));
     }
     return s*;
 }
 const double dev=1e-;
 inline double simpson(double l,double r,double fl,double fm,double fr){return (fl+*fm+fr)/*(r-l);}
 double integral(double l,double fl,double m,double fm,double r,double fr,double pre)
 {
     double lm=(l+m)/,rm=(m+r)/,flm=f(lm),frm=f(rm);
     double intl=simpson(l,m,fl,flm,fm),intr=simpson(m,r,fm,frm,fr);
     return abs(intl+intr-pre)<dev?intl+intr:integral(l,fl,lm,flm,m,fm,intl)+integral(m,fm,rm,frm,r,fr,intr);
 }
 int main(int argc, char *argv[])
 {
     double alp;scanf("%d%lf",&n,&alp);n++;
     for(int i=;i<=n;i++)scanf("%lf",&h[i]);
     for(int i=;i<n;i++)scanf("%lf",&c[i].r);c[n].r=;
     double s=1e10,e=-1e10;
     for(int i=;i<=n;i++)
     {
         h[i]+=h[i-];
         c[i].x=h[i]/tan(alp);
         s=min(s,c[i].x-c[i].r);
         e=max(e,c[i].x+c[i].r);
     }
     for(int i=;i<n;i++)
     {
         double dx=c[i+].x-c[i].x,dr=c[i].r-c[i+].r;
         if(abs(dx)<abs(dr)+eps)continue ;
         l[++lnum]=line(point(c[i].x+c[i].r/dx*dr,sqrt(c[i].r*c[i].r-(c[i].r/dx*dr)*(c[i].r/dx*dr)))
                       ,point(c[i+].x+c[i+].r/dx*dr,sqrt(c[i+].r*c[i+].r-(c[i+].r/dx*dr)*(c[i+].r/dx*dr))));
     }
     double m=(s+e)/,fm=f(m);
     printf("%.2lf\n",integral(s,,m,fm,e,,simpson(s,e,,fm,)));
     return ;
 }