for i, v in enumerate(heapq.merge(a, b)):
    c[i] = v

def larsmans(a, b):
    return np.array(sorted(set(a) | set(b)))

def larsmans_mod(a, b):
    return np.array(set.union(set(a), b))

def sebastian(a, b, kind='mergesort'):
    pass
combine two arrays and sort