POJ 1106 Transmitters(计算几何)

题目链接

切计算几何，感觉计算几何的算法还不熟。此题，枚举线段和圆点的直线，平分一个圆

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <cstdlib>
 #include <cmath>
 using namespace std;
 #define eps 1e-8
 struct point
 {
     double x,y;
 }p[];
 double dis(point p1,point p2)
 {
     return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));
 }
 double xmult(point p1,point p2,point p0)
 {
     return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
 }
 int main()
 {
     point r;
     double d;
     int n,m,i,j,ans,temp;
     while(scanf("%lf%lf%lf",&r.x,&r.y,&d)!=EOF)
     {
         if(d < ) break;
         scanf("%d",&n);
         m = ;
         for(i = ;i < n;i ++)
         {
             scanf("%lf%lf",&p[i].x,&p[i].y);
         }
         for(i = ;i < n;i ++)
         {
             if(dis(p[i],r) > d)
             continue;
             p[m++] = p[i];
         }
         ans = ;
         for(i = ;i < m;i ++)
         {
             temp = ;
             for(j = ;j < m;j ++)
             {
                 if(xmult(p[i],p[j],r) >= )
                 temp ++;
             }
             ans = max(ans,temp);
         }
         printf("%d\n",ans);
     }
     return ;
 }

。