An Improved Prefix-Free Regular-Expression Matching

We revisit the regular-expression matching problem with respect to prefix-freeness of the pattern. It is known that a prefix-free pattern gives only a linear number of matching substrings in the size of an input text. We improve the previous algorithm and suggest an efficient algorithm that finds all pairs (start, end) of start and end positions of all matching substrings with a single scan of the input when the pattern is a prefix-free regular expression.