KD tree - Difficulty in understanding a pointer

Question

I was reading a kd tree implementation in C.Here is some parts of it.The problem is in findmedian function.I dont understand the implementation of

*md = start +(end-start)/2;

...... -> Other irrelevant lines of code

struct kd_node_t
{
    double x[3];
    struct kd_node_t *left, *right;
};
struct kd_node_t* findmedian(struct kd_node_t *start, struct kd_node_t *end, int idx)
{
......
struct kd_node_t *p, *store, *md = start + (end - start) / 2;
......
}

Answer 1

Hm, what is implemented here is just the "half-way between the two pointers" start and end . If the implementation takes care that there is a meaningful value at this position in memory (which might be a median) then you're lucky, otherwise you get garbage...