Before revision:  Run-length Burrows-Wheeler transform (RLBWT) is a lossless data compression by a reversible permutation of an input string and run-length encoding, and it has become a popular research topic in string processing. R-index Gagie et al., ACM'20 is an efficient compressed index on RLBWTwhose space usage depends not on string length but the number of runs in an RLBWT, and it supports locate queries in an optimal time with \omega are two key functions for building indexes on RLBWT, and the best previous result computes LF and \phi^{-1} in O(\log \log n) time with O} (r) words for the number r of runs in the RLBWTof an input string.
After revision:  Run-length Burrows-Wheeler transform (RLBWT) is a lossless data compression by a reversible permutation of an input string and run-length encoding, and it has Gagie et al., ACM'20 is an efficient compressed index on RLBWTwhose space usage depends not on string length but the number of runs in an RLBWT, and it supports locate queries in an optimal time with \omega are two key functions for building indexes on RLBWT, and the best previous result computes LF and \phi^{-1} in O(\log \log n) time with O} (r) words for the number r of runs in the RLBWTof an input string.