【HDOJ】2150 Pipe

计算几何的基础题目。是时候刷刷计算几何了。

 /* 2150 */
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>

 typedef struct {
     int x, y;
 } Point_t;

 typedef struct {
     Point_t b, e;
     int v;
 } Pipe_t;

 #define MAXN 105

 Point_t points[MAXN];
 Pipe_t pipes[MAXN*];

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

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

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

 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(Pipe_t x, Pipe_t y) {
     if (x.v == y.v)
         return false;
     Point_t p1 = x.b, p2 = x.e, p3 = y.b, p4 = y.e;
     int d1 = direction(p3, p4, p1);
     int d2 = direction(p3, p4, p2);
     int d3 = direction(p1, p2, p3);
     int 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 main() {
     int n, m;
     int i, j, k;
     bool flag;

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

     while (scanf("%d", &n) != EOF) {
         m = ;
         flag = true;
         for (i=; i<n; ++i) {
             scanf("%d", &k);
             for (j=; j<k; ++j)
                 scanf("%d %d", &points[j].x, &points[j].y);
             for (j=; j<k; ++j)    {
                 pipes[m].b = points[j-];
                 pipes[m].e = points[j];
                 pipes[m].v = i;
                 ++m;
             }
         }
         for (i=; i<m; ++i) {
             for (j=i+; j<m; ++j) {
                 if (intersect(pipes[i], pipes[j])) {
                     flag = false;
                     goto _output;
                 }
             }
         }
         _output:
         if (flag)
             printf("No\n");
         else
             printf("Yes\n");
     }

     return ;
 }