-  regex + wildcard: regex: s: aa…..ab, p: a*…a*, wildcard: ?
    - extend: wildcard worst case: https://www.quora.com/How-do-I-solve-the-wildcard-matching-problem-in-Java

        - s: abcd, p: *e*f*g*h? abcd => swallow e

        - http://n00tc0d3r.blogspot.com/2013/05/wildcard-matching.html?
    - regular expression worst case
        - http://articles.leetcode.com/regular-expression-matching/
        - recursion worst case: time: O(2^n), space: O(n): s: aa…..ab, p: a*...a*