POJ 1127 Jack Straws(计算几何)

题目链接

抄的模版，居然1Y了。就是简单的线段相交+并查集。

 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 #define zero(x) (((x) > 0?(x):(-x))<eps)

 9 

10 struct point

11 {

12     double x,y;

13 };

14 struct line

15 {

16     point a,b;

17 };

18 int o[100];

19 line p[101];

20 int xmult(point p1,point p2,point p0)

21 {

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

23 }

24 int dot_online_in(point p,line l)

25 {

26     return zero(xmult(p,l.a,l.b))&&(l.a.x-p.x)*(l.b.x-p.x) < eps&&(l.a.y-p.y)*(l.b.y-p.y) < eps;

27 }

28 int dots_online(point p1,point p2,point p3)

29 {

30     return zero(xmult(p1,p2,p3));

31 }

32 int same_side(point p1,point p2,line l)

33 {

34     return xmult(l.a,p1,l.b)*xmult(l.a,p2,l.b) > eps;

35 }

36 int interset_in(line u,line v)

37 {

38     if(!dots_online(u.a,u.b,v.a)||!dots_online(u.a,u.b,v.b))

39     return !same_side(u.a,u.b,v)&&!same_side(v.a,v.b,u);

40 

41     return dot_online_in(u.a,v)||dot_online_in(u.b,v)||dot_online_in(v.a,u)||dot_online_in(v.b,u);

42 }

43 int find(int x)

44 {

45     while(x != o[x])

46     x = o[x];

47     return x;

48 }

49 void merge(int x,int y)

50 {

51     x = find(x);

52     y = find(y);

53     if(x != y)

54     o[x] = y;

55 }

56 int main()

57 {

58     int n,i,j,x,y;

59 

60     while(scanf("%d",&n)!=EOF)

61     {

62         if(n == 0) break;

63         for(i = 1;i <= n;i ++)

64         {

65             o[i] = i;

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

67         }

68         for(i = 1;i <= n;i ++)

69         {

70             for(j = i+1;j <= n;j ++)

71             {

72                 if(interset_in(p[i],p[j]))

73                 merge(i,j);

74             }

75         }

76         for(;;)

77         {

78             scanf("%d%d",&x,&y);

79             if(x == 0&&y == 0) break;

80             if(find(x) == find(y))

81             printf("CONNECTED\n");

82             else

83             printf("NOT CONNECTED\n");

84         }

85     }

86 

87     return 0;

88 }