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();
     }
 }