poj1106

极角排序扫一圈。

今天没什么状态写个水题减轻负罪感(大雾)

 #include <cstdio>

 #include <cmath>

 #include <cstring>

 #include <algorithm>

 #include <vector>

 using namespace std;

 typedef double db;

 const db eps = 1e-;

 const db pi = acos(-);

 int sign(db k){

     if (k>eps) return ; else if (k<-eps) return -; return ;

 }

 int cmp(db k1,db k2){return sign(k1-k2);}

 struct point{

     db x,y,ang;

     point operator + (const point &k1) const{return (point){k1.x+x,k1.y+y};}

     point operator - (const point &k1) const{return (point){x-k1.x,y-k1.y};}

     point operator * (db k1) const{return (point){x*k1,y*k1};}

     point operator / (db k1) const{return (point){x/k1,y/k1};}

     int operator == (const point &k1) const{return cmp(x,k1.x)==&&cmp(y,k1.y)==;}

     db abs(){ return sqrt(x*x+y*y);}

     db dis(point k1){return ((*this)-k1).abs();}

     db getw(){return atan2(y,x);}

 };

 struct circle{

     point o;db r;

     int inside(point k){return cmp(r,o.dis(k))>=;}

 }c;

 vector<point> v;

 bool cmp2(point a,point b){

     return a.ang<b.ang;

 }

 int n;point t;

 int main(){

     while (scanf("%lf%lf%lf",&c.o.x,&c.o.y,&c.r)&&c.r>){

     //scanf("%lf%lf%lf",&c.o.x,&c.o.y,&c.r);

         scanf("%d",&n);

         while (n--){

             scanf("%lf%lf",&t.x,&t.y);

             if(c.inside(t)){

                 t.ang = (c.o-t).getw();

                 v.push_back(t);

                 v.push_back({t.x,t.y,t.ang+*pi});

             }

         }

         sort(v.begin(),v.end(),cmp2);

         int m = v.size()/;

         int ans = ;

         for(int l=,r=;l<m;l++){

             while (r<*m&&v[r].ang-v[l].ang<=pi)

                 r++;

             ans=max(ans,r-l);

         }

         printf("%d\n",ans);

         v.clear();

     }

 }