记录编号	26927	评测结果	AAAAAAAAAA
题目名称	打蚊子	最终得分	100
用户昵称	PurpleShadow	是否通过	通过
代码语言	C++	运行时间	1.991 s
提交时间	2011-07-29 17:18:10	内存使用	0.29 MiB

#include <cstdio>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;
const int N=2010;
const double pi=acos(-1.0);
int n,R;
struct node
{
	double r;
	int o;
	bool operator<(const node &t)const
	{return r<t.r;}
	node(const double &_r,const int &_o):r(_r),o(_o){}
};
struct point
{double x,y;} p[N];
vector<node> A;
inline double dis(const point &a,const point &b)
{return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}
inline double GetAngle(const point &a,const point &b)
{
	double ki=atan2(b.x-a.x,b.y-a.y);
	return ki<0?2*pi+ki:ki;
}
void solve()
{
	int i,j,sum,ans=1;
	double dist,thi,delta;
	for (i=1;i<=n;++i)
	{
		A.clear();
		for (j=1;j<=n;++j)
		{
			if (i==j) continue;
			if ((dist=dis(p[i],p[j]))>2*R) continue;
			thi=GetAngle(p[i],p[j]);
			delta=acos(dist/2/R);
			A.push_back(node(thi-delta,1));
			A.push_back(node(thi+delta,-1));
		}
		if (A.size()<ans*2) continue;
		sort(A.begin(),A.end());
		sum=1;
		for (vector<node>::iterator vt=A.begin();vt!=A.end();++vt)
		{
			sum+=vt->o;
			if (sum>ans) ans=sum;
		}
	}
	printf("%d\n",ans);
}
int main()
{
freopen("fight.in","r",stdin);
freopen("fight.out","w",stdout);
	scanf("%d%d",&n,&R);
	for (int i=1;i<=n;++i)
		scanf("%lf%lf",&p[i].x,&p[i].y);
	solve();
	return 0;
}