O(n n)-time text compression by LZ-style longest first substitution

06/13/2018

∙

by   Akihiro Nishi, et al.

∙

0

∙

share

Mauer et al. [A Lempel-Ziv-style Compression Method for Repetitive Texts, PSC 2017] proposed a hybrid text compression method called LZ-LFS which has both features of Lempel-Ziv 77 factorization and longest first substitution. They showed that LZ-LFS can achieve better compression ratio for repetitive texts, compared to some state-of-the-art compression algorithms. The drawback of Mauer et al.'s method is that their LZ-LFS compression algorithm takes O(n^2) time on an input string of length n. In this paper, we show a faster LZ-LFS compression algorithm that works in O(n n) time. We also propose a simpler version of LZ-LFS that can be computed in O(n) time.