Find simplest regular expression matching all given strings

Question

Is there an algorithm that can produce a regular expression (maybe limited to a simplified grammar) from a set of strings such that the evaluation of all possible strings th

Answer 1

You can try to use Aho-Corasick algorithm to create a finite state machine from the input strings, after which it should be somewhat easy to generate the simplified regex. Your input strings as example:

h_q1_a
h_q1_b
h_q1_c
h_p2_a
h_p2_b
h_p2_c

will generate a finite machine that most probably look like this:

      [h_]         <-level 0
     /   \
  [q1]  [p2]       <-level 1
     \   /
      [_]          <-level 2
      /\  \
     /  \  \
    a    b  c      <-level 3

Now for every level/depth of the trie all the stings (if multiple) will go under OR brackets, so

h_(q1|p2)_(a|b|c)
L0   L1  L2  L3