AoC Day11 Part2 DP

static uint64_t dp(device *d, device *t, cache **kache) {
    if (d == t) {
        return 1;
    } else {
        cache *ca = NULL;
        HASH_FIND(hh, *kache, &d, sizeof(device *), ca);
        if (ca != NULL) {
            return ca->n;
        }
        ca = (cache *)malloc(sizeof(cache));
        ca->n = 0;
        ca->d = d;
        for (int i = 0; i < d->n; i++) {
            device *d0 = d->os[i];
            ca->n += dp(d0, t, kache);
        }
        HASH_ADD(hh, *kache, d, sizeof(device *), ca);
        return ca->n;
    }
}