计算几何的基础题目。是时候刷刷计算几何了。
1 /* 2150 */ 2 #include <cstdio> 3 #include <cstring> 4 #include <cstdlib> 5 6 typedef struct { 7 int x, y; 8 } Point_t; 9 10 typedef struct { 11 Point_t b, e; 12 int v; 13 } Pipe_t; 14 15 #define MAXN 105 16 17 Point_t points[MAXN]; 18 Pipe_t pipes[MAXN*30]; 19 20 int max(int a, int b) { 21 return a>b ? a:b; 22 } 23 24 int min(int a, int b) { 25 return a<b ? a:b; 26 } 27 28 29 int direction(Point_t p0, Point_t p1, Point_t p2) { 30 return (p1.x-p0.x)*(p2.y-p0.y) - (p2.x-p0.x)*(p1.y-p0.y); 31 } 32 33 bool onSegment(Point_t p0, Point_t p1, Point_t p2) { 34 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))) ) 35 return true; 36 return false; 37 } 38 39 bool intersect(Pipe_t x, Pipe_t y) { 40 if (x.v == y.v) 41 return false; 42 Point_t p1 = x.b, p2 = x.e, p3 = y.b, p4 = y.e; 43 int d1 = direction(p3, p4, p1); 44 int d2 = direction(p3, p4, p2); 45 int d3 = direction(p1, p2, p3); 46 int d4 = direction(p1, p2, p4); 47 if ( ((d1>0 && d2<0) || (d1<0 && d2>0)) && ((d3<0 && d4>0) || (d3>0 && d4<0)) ) 48 return true; 49 else if (d1==0 && onSegment(p3, p4, p1)) 50 return true; 51 else if (d2==0 && onSegment(p3, p4, p2)) 52 return true; 53 else if (d3==0 && onSegment(p1, p2, p3)) 54 return true; 55 else if (d4==0 && onSegment(p1, p2, p4)) 56 return true; 57 else 58 return false; 59 } 60 61 int main() { 62 int n, m; 63 int i, j, k; 64 bool flag; 65 66 #ifndef ONLINE_JUDGE 67 freopen("data.in", "r", stdin); 68 #endif 69 70 while (scanf("%d", &n) != EOF) { 71 m = 0; 72 flag = true; 73 for (i=0; i<n; ++i) { 74 scanf("%d", &k); 75 for (j=0; j<k; ++j) 76 scanf("%d %d", &points[j].x, &points[j].y); 77 for (j=1; j<k; ++j) { 78 pipes[m].b = points[j-1]; 79 pipes[m].e = points[j]; 80 pipes[m].v = i; 81 ++m; 82 } 83 } 84 for (i=0; i<m; ++i) { 85 for (j=i+1; j<m; ++j) { 86 if (intersect(pipes[i], pipes[j])) { 87 flag = false; 88 goto _output; 89 } 90 } 91 } 92 _output: 93 if (flag) 94 printf("No "); 95 else 96 printf("Yes "); 97 } 98 99 return 0; 100 }