Deep Holes and MDS Extensions of Reed–Solomon Codes

We study the problem of classifying deep holes of Reed-Solomon codes. We show that this problem is equivalent to the problem of classifying maximum distance separable (MDS) extensions of Reed-Solomon codes by one digit. This equivalence allows us to improve recent results on the former problem. In particular, we classify deep holes of Reed-Solomon codes of dimension greater than half the alphabet size. We also give a complete classification of deep holes of Reed-Solomon codes with redundancy three in all dimensions.