Packing several characters into one computer word is a simple and natural way
to compress the representation of a string and to speed up its processing.
Exploiting this idea, we propose an index for a packed string, based on a {\em
sparse suffix tree} \cite{KU-96} with appropriately defined suffix links.
Assuming, under the standard unit-cost RAM model, that a word can store up to
logĻān characters (Ļ the alphabet size), our index takes
O(n/logĻān) space, i.e. the same space as the packed string itself.
The resulting pattern matching algorithm runs in time O(m+r2+rā occ),
where m is the length of the pattern, r is the actual number of characters
stored in a word and occ is the number of pattern occurrences