1 #include <iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 #include<stdlib.h> 6 #include<vector> 7 #include<cmath> 8 #include<queue> 9 #include<set>10 using namespace std;11 #define N 31012 #define LL long long13 #define INF 0xfffffff14 const double eps = 1e-8;15 const double pi = acos(-1.0);16 const double inf = ~0u>>2;17 struct point18 {19     double x,y;20     point(double x = 0,double y =0 ):x(x),y(y){}21 }p[N];22 double dis(point a,point b)23 {24     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));25 }26 point getcircle(point p1,point p2)27 {28     point mid = point((p1.x+p2.x)/2,(p2.y+p1.y)/2);29     double angle = atan2(p2.y-p1.y,p2.x-p1.x);30     double d = sqrt(1.0-dis(p1,mid)*dis(p1,mid));31     return point(mid.x+d*sin(angle),mid.y-d*cos(angle));32 }33 int dcmp(double x)34 {35     if(fabs(x)<eps)return 0;36     else return x<0?-1:1;37 }38 int main()39 {40     int i,j,n;41     while(scanf("%d",&n)&&n)42     {43         for(i = 1 ;i <= n; i++)44         scanf("%lf%lf",&p[i].x,&p[i].y);45         int maxz = 1;46         for(i = 1; i <= n; i++)47             for(j = i+1 ; j <= n ;j++)48             {49                 if(dis(p[i],p[j])>2.0) continue;50                 int tmax = 0;51                 point cir = getcircle(p[i],p[j]);52                 for(int g =  1; g <= n ;g++)53                 {54                     if(dcmp(dis(cir,p[g])-1.0)>0)55                     continue;56                     tmax++;57                 }58                 maxz = max(maxz,tmax);59             }60         printf("%d\n",maxz);61     }62     return 0;63 }

 1 #include <iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 #include<stdlib.h> 6 #include<vector> 7 #include<cmath> 8 #include<queue> 9 #include<set>10 using namespace std;11 #define N 31012 #define LL long long13 #define INF 0xfffffff14 const double eps = 1e-8;15 const double pi = acos(-1.0);16 const double inf = ~0u>>2;17 struct point18 {19     double x,y;20     point(double x = 0,double y =0 ):x(x),y(y) {}21 } p[N];22 struct node23 {24     double ang;25     int in;26 } arc[N*N];27 double dis(point a,point b)28 {29     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));30 }31 int dcmp(double x)32 {33     if(fabs(x)<eps)return 0;34     else return x<0?-1:1;35 }36 bool cmp(node a,node b)37 {38     if(dcmp(a.ang-b.ang)==0)39         return a.in>b.in;40     return dcmp(a.ang-b.ang)<0;41 }42 int main()43 {44     int i,j,n;45     while(scanf("%d",&n)&&n)46     {47         for(i = 1 ; i <= n; i++)48             scanf("%lf%lf",&p[i].x,&p[i].y);49         int g = 0;50         int ans = 0,maxz = 1;51         for(i = 1; i <= n ; i++)52         {53             ans = 0;54             g = 0;55             for(j = 1; j <= n ; j++)56             {57                 if(dis(p[i],p[j])>2.0) continue;58                 double ang1 = atan2(p[j].y-p[i].y,p[j].x-p[i].x);59                 double ang2 = acos(dis(p[i],p[j])/2);60                 arc[++g].ang = ang1-ang2;//这里角度的算法很巧妙61                 arc[g].in = 1;62                 arc[++g].ang = ang1+ang2;63                 arc[g].in = -1;64             }65             sort(arc+1,arc+g+1,cmp);66 67             //cout<<g<<endl;68             for(j = 1 ; j <= g;j++)69             {70                 ans+=arc[j].in;71                 maxz = max(maxz,ans);72             }73         }74         printf("%d\n",maxz);75     }76     return 0;77 }