判断点与三角形的关系

1566阅读　0评论2011-05-18　onezeroone
分类：C/C++

  1. #include <stdio.h>
  2. #include <math.h>

  4. struct _point {
  5.     double x;
  6.     double y;
  7. };
  8. typedef struct _point point;

  10. struct _triangle {
  11.     point a;
  12.     point b;
  13.     point c;
  14. };
  15. typedef struct _triangle triangle;

  17. int check(triangle t, point p);

  19. int
  20. main(void)
  21. {
  22.     triangle t;
  23.     t.a.x = 1;
  24.     t.a.y = 1;
  25.     t.b.x = 3;
  26.     t.b.y = 1;
  27.     t.c.x = 3;
  28.     t.c.y = 2;

  30.     point p;
  31.     p.x = 2;
  32.     p.y = 2;

  34.     point q;
  35.     q.x = 3;
  36.     q.y = 3;

  38.     point r;
  39.     r.x = 2;
  40.     r.y = 1;

  42.     printf("Res: %d\n", check(t, p));
  43.     printf("Res: %d\n", check(t, q));
  44.     printf("Res: %d\n", check(t, r));

  46.     return 0;
  47. }

  49. double
  50. distance(point p1, point p2)
  51. {
  52.     double res;
  53.     double x = p1.x - p2.x;
  54.     double y = p1.y - p2.y;
  55.     res = sqrt(x*x + y*y);

  57.     return res;
  58. }

  60. double
  61. area(point p1, point p2, point p3)
  62. {
  63.     double res;
  64.     double a = distance(p1, p2);
  65.     double b = distance(p2, p3);
  66.     double c = distance(p3, p1);
  67.     double p = (a + b + c) / 2;
  68.     res = sqrt(p*(p-a)*(p-b)*(p-c));
  69.     
  70.     return res;
  71. }

  73. int
  74. check(triangle t, point p)
  75. {
  76.     double res;
  77.     double base = area(t.a, t.b, t.c);
  78.     double x = area(t.a, t.b, p);
  79.     double y = area(t.b, t.c, p);
  80.     double z = area(t.c, t.a, p);

  82.     if (base <= (x+y+z))
  83.         if (0 != x && 0 != y && 0 != z)
  84.             return 1;
  85.         else
  86.             return 0;
  87.     else
  88.         return (-1);
  89. }

上一篇：单实例模式1
下一篇：字符串连接返回串尾