A relatively simple and readable C (C99) implementation of Vantage Point tree search algorithm.
The VP tree algorithm doesn't need to know coordinates of items, only distances between them. It can efficiently search multi-dimensional spaces and abstract things as long as you can define similarity between them (e.g. points, colors, and even images).
Please see vp.c for details.
```C
typedef struct point {float x,y;} point;
float get_distance(const void *a, const void *b) { float dx = ((point *)a)->x - ((point *)b)->x; float dy = ((point *)a)->y - ((point *)b)->y;
return sqrt(dx*dx + dy*dy); // sqrt is required
}
int main(void) {
// The library operates on pointers to elements
point *points[] = {&(point){2,3}, &(point){0,1}, &(point){4,5}};
vp_handle *vp = vp_init((void**)points, 3, get_distance);
int index = vp_find_nearest(vp, &(point){1,2});
printf("The nearest point is at (%f,%f)\n", points[index]->x, points[index]->y);
vp_free(vp);
} ```