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

 1 #include <iostream>

 2 #include <cstring>

 3 #include <cstdio>

 4 #include <cstdlib>

 5 #include <cmath>

 6 using namespace std;

 7 #define eps 1e-8

 8 struct point

 9 {

10     double x,y;

11 }p[201];

12 double dis(point p1,point p2)

13 {

14     return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));

15 }

16 double xmult(point p1,point p2,point p0)

17 {

18     return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);

19 }

20 int main()

21 {

22     point r;

23     double d;

24     int n,m,i,j,ans,temp;

25     while(scanf("%lf%lf%lf",&r.x,&r.y,&d)!=EOF)

26     {

27         if(d < 0) break;

28         scanf("%d",&n);

29         m = 0;

30         for(i = 0;i < n;i ++)

31         {

32             scanf("%lf%lf",&p[i].x,&p[i].y);

33         }

34         for(i = 0;i < n;i ++)

35         {

36             if(dis(p[i],r) > d)

37             continue;

38             p[m++] = p[i];

39         }

40         ans = 0;

41         for(i = 0;i < m;i ++)

42         {

43             temp = 0;

44             for(j = 0;j < m;j ++)

45             {

46                 if(xmult(p[i],p[j],r) >= 0)

47                 temp ++;

48             }

49             ans = max(ans,temp);

50         }

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

52     }

53     return 0;

54 }

 

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