10. Regular Expression Matching

[axross]

Recurrence relation:

f(si, pi) = { { true  IF isOnlyOptionalPatternLeft(si, pi) 
                false OTHERWISE                                                        } IF si == s.length
              { isHeadMatch(si, pi) AND f(si + 1, pi) OR f(si, pi + 2) IF p[pi] == "*" 
                isHeadMatch(si, pi) AND f(si + 1, pi + 1)              OTHERWISE       } IF pi != p.length
              false                                                                      OTHERWISE         }