1 条题解
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0
C++ :
#include<cstdio> #include<iostream> #include<cstring> #include<cmath> #include<cstdlib> #define d double #define ld long double using namespace std; const int maxn=323; const d eps=1e-7; struct poi{ int x,y; }a[maxn]; d ansx,ansaddy,nowx,nowy;int posl,posr; int i,j,k,n,m; int ra,fh;char rx; inline int read(){ rx=getchar(),ra=0,fh=1; while((rx<'0'||rx>'9')&&rx!='-')rx=getchar(); if(rx=='-')fh=-1,rx=getchar(); while(rx>='0'&&rx<='9')ra*=10,ra+=rx-48,rx=getchar();return ra*fh; } inline d randlf(){ return rand()%10000/10000.0; } bool judge(){ int i; for(i=1;i<posl;i++)if((nowy-a[i].y)*(nowx-a[i+1].x)>(nowy-a[i+1].y)*(nowx-a[i].x)) return 0; for(i=posr;i<n;i++)if((a[i].y-nowy)*(a[i+1].x-nowx)>(a[i+1].y-nowy)*(a[i].x-nowx)) return 0; return 1; } inline d geth(){ int L=1,R=n,MID;ld sy,l,r,mid; while(L<R) if(a[(MID=(L+R+1)>>1)].x<=nowx)L=MID;else R=MID-1; posl=L,posr=L+1; if(a[L].x==nowx)posl--,sy=a[L].y;else sy=a[posl].y+(a[posr].y-a[posl].y)*(nowx-a[posl].x)/(a[posr].x-a[posl].x); l=0,r=1e11;//printf("geth: x:%.8lf l r:%d %d sy:%.3lf\n",nowx,a[posl].x,a[posr].x,sy); while(l+1e-7<r){ mid=(l+r)/2;nowy=sy+mid; if(judge())r=mid;//,printf("success: %.2lf %.2lf %.9lf\n",nowx,(d)sy,(d)mid); else l=mid;//,printf("failed: %.2lf %.2lf %.9lf %.9lf %.9lf\n",nowx,(d)sy,(d)mid,(d)l,(d)r); } if(l<ansaddy)ansaddy=l,ansx=nowx; return l; }//<n*64 inline void SA(){ d T=a[n].x-a[1].x,prex,tmpaddy,nowaddy; nowx=ansx=(a[n].x+a[1].x)/2.0;nowaddy=geth();//printf(" %.2lf\n",nowx); while(T>1e-5){ T*=0.99;//printf("! %d\n",fabs(nowaddy-geth())<=eps); prex=nowx,nowx+=T*(randlf()*2-1); // printf("try:%.3lf\n",nowx); if(nowx<a[1].x||nowx>a[n].x){nowx=prex;T/=0.991;continue;} tmpaddy=geth(); if(tmpaddy>nowaddy&&exp((nowaddy-tmpaddy)/T)<randlf()) nowx=prex; else nowaddy=tmpaddy; } for(int i=1;i<=1023;i++){ nowx=ansx+T*(randlf()*2-1);//printf("try1:%.3lf\n",nowx); if(nowx<a[1].x||nowx>a[n].x)continue; geth(); } } int main(){ n=read();srand(233); // srand(19980406); for(i=1;i<=n;i++)a[i].x=read(); for(i=1;i<=n;i++)a[i].y=read();ansaddy=1e11; SA(); printf("%.3lf\n",ansaddy+eps);//printf("ansx: %.3lf\n",ansx); return 0; }
- 1
信息
- ID
- 1008
- 时间
- 1000ms
- 内存
- 128MiB
- 难度
- (无)
- 标签
- 递交数
- 0
- 已通过
- 0
- 上传者