Computing q-gram Frequencies on Collage Systems
  Collage systems are a general framework for representing outputs of various text compression algorithms. We consider the all $q$-gram frequency problem on compressed string represented as a collage system, and present an $O((q+h\log n)n)$-time $O(qn)$-space algorithm for calculating the frequencies for all $q$-grams that occur in the string. Here, $n$ and $h$ are respectively the size and height of the collage system. 
Keisuke Goto, Hideo Bannai, Shunsuke Inenaga, Masayuki Takeda
cs.DS