hdu 1558 Segment set

http://acm.hdu.edu.cn/showproblem.php?pid=1558

先判断线段相交，然后用并查集合并。

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #define maxn 20000

 5 using namespace std;

 6 

 7 int num[maxn],f[maxn];

 8 

 9 struct point

10 {

11     double x,y;

12 };

13 struct line

14 {

15     point p1,p2;

16 }p[maxn];

17 

18 

19 void inti()

20 {

21     for(int i=0; i<=maxn; i++)

22     {

23         f[i]=i;

24         num[i]=1;

25     }

26 }

27 double det(point a,point b,point c)

28 {

29     return (c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);

30 }

31 

32 int find1(int x)

33 {

34     if(x==f[x]) return x;

35     return f[x]=find1(f[x]);

36 }

37 

38 void merge1(int a,int b)

39 {

40     int fa=find1(a);

41     int fb=find1(b);

42     if(fa!=fb)

43     {

44         f[fa]=fb;

45         num[fb]+=num[fa];

46     }

47 }

48 

49 bool Isintsert(line u,line v)

50 {

51     return (det(v.p1,u.p2,u.p1)*det(u.p2,v.p2,u.p1)>=0)&&(det(u.p1,v.p2,v.p1)*det(v.p2,u.p2,v.p1)>=0)&&

52     (max(u.p1.x,u.p2.x)>=min(v.p1.x,v.p2.x))&&

53     (max(v.p1.x,v.p2.x)>=min(u.p1.x,u.p2.x))&&

54     (max(u.p1.y,u.p2.y)>=min(v.p1.y,v.p2.y))&&

55     (max(v.p1.y,v.p2.y))>=min(u.p1.y,u.p2.y);

56 }

57 

58 int main()

59 {

60     int t,n,k1;

61     char ch;

62     scanf("%d",&t);

63     while(t--)

64     {

65         inti();

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

67         getchar();

68         int t1=1;

69         for(int i=0; i<n; i++)

70         {

71             scanf("%c",&ch);

72             if(ch=='P')

73             {

74                 scanf("%lf%lf%lf%lf",&p[t1].p1.x,&p[t1].p1.y,&p[t1].p2.x,&p[t1].p2.y);

75                 t1++;

76                 for(int j=1; j<t1-1; j++)

77                 {

78                     int f2=find1(t1-1); int f3=find1(j);

79                     if(f2!=f3&&Isintsert(p[j],p[t1-1]))

80                     {

81                         merge1(j,t1-1);

82                     }

83                 }

84             }

85             else if(ch=='Q')

86             {

87                 scanf("%d",&k1);

88                 int k2=find1(k1);

89                 printf("%d\n",num[k2]);

90             }

91             getchar();

92             

93         }

94         if(t!=0) printf("\n");

95     }

96     return 0;

97 }

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