FA to regex, state removal method

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C#

Here's a Christmas Eve brain teaser.

FA state to regular expression by the state removal method

Generating regular expression from Finite Automata - GeeksforGeeks[^]

Using the first method at that link.

abcd(ef)*g

q0:
        abcd -> q1

q1:
        ef -> q1
        g -> q2

*q2:

The idea here is to turn the above qX set of states back into a regular expression that is equivalent to the one at the top.

You can see I've already done some of it. the string "abcd" was originally several states/transitions, and "ef" was two.

The main trouble is states like q1 where there is more than one transition. I think I can handle loops (maybe?) but right now this part is getting me.

What I have tried:

GitHub - codewitch-honey-crisis/FAToRegex: A testbed for FA to Regex via state removal in C# (work in progress)[^]

See Program.cs for the meat. The rest is just support. The function of interest is ToRegex().