【HDOJ】1558 Segment set

并查集+计算几何。

 /* 1558 */
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>

 #define MAXN 1005

 typedef struct {
     double x, y;
 } Point_t;

 typedef struct {
     Point_t b, e;
 } Seg_t;

 Seg_t segs[MAXN];
 int pre[MAXN];
 int ans[MAXN];

 int max(int a, int b) {
     return a>b ? a:b;
 }

 int min(int a, int b) {
     return a<b ? a:b;
 }

 double direction(Point_t p0, Point_t p1, Point_t p2) {
     return (p1.x-p0.x)*(p2.y-p0.y) - (p1.y-p0.y)*(p2.x-p0.x);
 }

 bool onSegment(Point_t p0, Point_t p1, Point_t p2) {
     if ( (min(p0.x, p1.x)<=p2.x && p2.x<=max(p0.x, p1.x)) &&\
          (min(p0.y, p1.y)<=p2.y && p2.y<=max(p0.y, p1.y)) )
         return true;
     return false;
 }

 bool intersect(Seg_t x, Seg_t y) {
     Point_t p1 = x.b, p2 = x.e, p3 = y.b, p4 = y.e;
     double d1 = direction(p3, p4, p1);
     double d2 = direction(p3, p4, p2);
     double d3 = direction(p1, p2, p3);
     double d4 = direction(p1, p2, p4);
     if ( ((d1> && d2<) || (d1< && d2>)) &&\
          ((d3> && d4<) || (d3< && d4>)) )
         return true;
     else if (d1== && onSegment(p3, p4, p1))
         return true;
     else if (d2== && onSegment(p3, p4, p2))
         return true;
     else if (d3== && onSegment(p1, p2, p3))
         return true;
     else if (d4== && onSegment(p1, p2, p4))
         return true;
     else
         return false;
 }

 int find(int x) {
     if (x == pre[x])
         return x;
     pre[x] = find(pre[x]);
     return pre[x];
 }

 void merge(int x, int y) {
     int fx = find(x);
     int fy = find(y);
     if (fx != fy) {
         pre[fy] = fx;
         ans[fx] += ans[fy];
         ans[fy] = ;
     }
 }

 int main() {
     int t, n, m;
     int i, j, k;
     char cmd[];

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
     #endif

     scanf("%d", &t);
     while (t--) {
         scanf("%d", &n);
         for (i=; i<=n; ++i) {
             pre[i] = i;
             ans[i] = ;
         }
         m = ;
         while (n--) {
             scanf("%s", cmd);
             if (cmd[] == 'P') {
                 scanf("%lf%lf%lf%lf", &segs[m].b.x, &segs[m].b.y, &segs[m].e.x, &segs[m].e.y);
                 for (i=; i<m; ++i) {
                     if (intersect(segs[i], segs[m]))
                         merge(i, m);
                 }
                 ++m;
             } else {
                 scanf("%d", &j);
                 k = find(j);
                 printf("%d\n", ans[k]);
             }
         }
         if (t)
             printf("\n");
     }

     return ;
 }