bzoj 2178 自适应Simpson积分

 #include<iostream>
 #include<algorithm>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<cmath>
 using namespace std;
 int n;
 const double eps = 1e-;
 struct node
 {
     double x,y,r;
 }b[],a[];int cnt;
 bool cmp1(node aa,node bb)
 {
     return aa.r<bb.r;
 }
 bool v[];
 double dis(int x,int y)
 {
     return sqrt((b[x].x-b[y].x)*(b[x].x-b[y].x)+(b[x].y-b[y].y)*(b[x].y-b[y].y));
 }
 double lmin,rmax;
 pair<double,double>q[];
 double mx(double x,double y)
 {
     return x<y?y:x;
 }
 double f(double x)
 {
     int top=;double len=;
     for(int i=;i<=cnt;i++)
     {
         double xx=fabs(a[i].x-x);
         if(fabs(xx)<=a[i].r)
         {
             double ww=sqrt(a[i].r*a[i].r-xx*xx);
             q[++top].first=a[i].y-ww;
             q[top].second=a[i].y+ww;
         }
     }
     sort(q+,q+top+);len+=q[].second-q[].first;
     double rs=q[].second;
     for(int i=;i<=top;i++)if(q[i].second>rs)len+=q[i].second-mx(q[i].first,rs),rs=q[i].second;
     return len;
 }
 double asr(double l,double mid,double r,double A,double B,double C)
 {
     double s=((r-l)/)*(A+*B+C),lf=f((l+mid)/),rf=f((mid+r)/);
     double ls=((mid-l)/)*(A+B+*lf),rs=((r-mid)/)*(B+C+*rf);
     if(fabs(s-ls-rs)<=eps)return s;
     return asr(l,(l+mid)/,mid,A,lf,B)+asr(mid,(r+mid)/,r,B,rf,C);
 }
 int main()
 {
     scanf("%d",&n);
     for(int i=;i<=n;i++)
     {
         scanf("%lf%lf%lf",&b[i].x,&b[i].y,&b[i].r);
         lmin=min(lmin,b[i].x-b[i].r);rmax=max(rmax,b[i].x+b[i].r);
     }
     sort(b+,b+n+,cmp1);
     for(int i=;i<=n;i++)
     {
         for(int j=;j<i;j++)
         {
             if(dis(i,j)<=b[i].r-b[j].r)v[j]=;
         }
     }
     for(int i=;i<=n;i++)if(!v[i])a[++cnt]=b[i];
     printf("%.3f\n",asr(lmin,(lmin+rmax)/,rmax,,f((lmin+rmax)/),));
     return ;
 }