Shortest unique substring queries on run-length encoded strings

We consider the problem of answering shortest unique substring (SUS) queries on run-length encoded strings. For a string S, a unique substring u = S[i..j] is said to be a shortest unique substring (SUS) of S containing an interval [s, t] (i ≤ s ≤ t ≤ j) if for any i0 ≤ s ≤t ≤j0 with j - i > j0 - i0, S[i0..j0] occurs at least twice in S. Given a run-length encoding of size m of a string of length N, we show that we can construct a data structure of size O(m + πs(N,m)) in O(mlogm + πc(N,m)) time such that queries can be answered in O(πq(N,m) + k) time, where k is the size of the output (the number of SUSs), and πs(N,m), πc(N,m), πq(N,m) are, respectively, the size, construction time, and query time for a predecessor/successor query data structure of m elements for the universe of [1,N]. Using the data structure by Beam and Fich (JCSS 2002), this results in a data structure of O(m) space that is constructed in O(mlogm) time, and answers queries in O( √ log m/log logm + k) time.