mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
89 lines
2.3 KiB
C++
89 lines
2.3 KiB
C++
#include<iostream>
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#include<math.h>
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#include<cstring>
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#include<stdio.h>
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#include<algorithm>
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using namespace std;
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#define offset 100
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#define eps 1e-8
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#define PI acos(-1.0)
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#define MAXN 105
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#define zero(x) (((x)>0? (x):-(x))<eps)
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#define _sign(x) ((x)>eps? 1:((x)<-eps? 2:0))
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struct point
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{
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double x;
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double y;
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point(const double &x = 0, const double &y = 0):x(x), y(y) {}
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void in()
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{
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scanf("%lf %lf", &x, &y);
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}
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void out()const
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{
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printf("%.2f %.2f\n",x, y);
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}
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};
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double xmult(point p1,point p2,point p0)
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{
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return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
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}
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double dis(point a, point b)
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{
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return sqrt( (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y) ) ;
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}
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point p1,p2;
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int graham_cp(const void* a,const void* b)
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{
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double ret=xmult(*((point*)a),*((point*)b),p1);
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return zero(ret)?(xmult(*((point*)a),*((point*)b),p2)>0?1:-1):(ret>0?1:-1);
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}
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void _graham(int n,point* p,int& s,point* ch)
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{
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int i,k=0;
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for (p1=p2=p[0],i=1; i<n; p2.x+=p[i].x,p2.y+=p[i].y,i++)
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if (p1.y-p[i].y>eps||(zero(p1.y-p[i].y)&&p1.x>p[i].x))
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p1=p[k=i];
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p2.x/=n,p2.y/=n;
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p[k]=p[0],p[0]=p1;
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qsort(p+1,n-1,sizeof(point),graham_cp);
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for (ch[0]=p[0],ch[1]=p[1],ch[2]=p[2],s=i=3; i<n; ch[s++]=p[i++])
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for (; s>2&&xmult(ch[s-2],p[i],ch[s-1])<-eps; s--);
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}
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int graham(int n,point* p,point* convex,int maxsize=1,int dir=1)
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{
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point* temp=new point[n];
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int s,i;
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_graham(n,p,s,temp);
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for (convex[0]=temp[0],n=1,i=(dir?1:(s-1)); dir?(i<s):i; i+=(dir?1:-1))
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if (maxsize||!zero(xmult(temp[i-1],temp[i],temp[(i+1)%s])))
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convex[n++]=temp[i];
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delete []temp;
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return n;
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}
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int main()
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{
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int T, N, D, cas = 1;
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scanf("%d",&T);
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while(T--)
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{
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point P[MAXN];
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point c[MAXN];
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scanf("%d%d",&N,&D);
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for(int i = 0; i < N; i ++)
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P[i].in();
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double ans = 0 ;
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if(N>2)
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{
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int num = graham(N,P,c);
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for(int i = 0; i < num-1; i ++)
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{
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ans+=dis(c[i],c[i+1]);
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}
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ans+=dis(c[0],c[num-1]);
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}
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else ans = dis(P[0],P[1])*2;
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printf("Case #%d: %.4lf\n",cas++,ans/(PI*D));
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}
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}
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