Figure 3: The LF Mapping datastructures Occ counting the number occurrences of each character before each position, and C , the number of characters less than each character. The idea is to start at the end of the query and iteratively prepend characters, while keeping track of the range of the suffix array that corresponds to the current suffix of the query. Figure 5: The red boxes indicate that the set of characters following matches (cyan) of Q in the forward suffix array (left) is the same as the set following the matches of Q in the reverse suffix array (right).