Practical linear-time O(1)-workspace suffix sorting for constant alphabets

This article presents an O(n)-time algorithm called SACA-K for sorting the suffixes of an input string T[0, n-1] over an alphabet A[0, K-1]. The problem of sorting the suffixes of T is also known as constructing the suffix array (SA) for T. The theoretical memory usage of SACA-K is n log K + n log n + K log n bits. Moreover, we also have a practical implementation for SACA-K that uses n bytes + (n + 256) words and is suitable for strings over any alphabet up to full ASCII, where a word is log n bits. In our experiment, SACA-K outperforms SA-IS that was previously the most time- and space-efficient linear-time SA construction algorithm (SACA). SACA-K is around 33% faster and uses a smaller deterministic workspace of K words, where the workspace is the space needed beyond the input string and the output SA. Given K=O(1), SACA-K runs in linear time and O(1) workspace. To the best of our knowledge, such a result is the first reported in the literature with a practical source code publicly available.