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 ",num[k2]); 90 } 91 getchar(); 92 93 } 94 if(t!=0) printf(" "); 95 } 96 return 0; 97 }