- Subtraction Quantify with care.
- Typist With apologies to Dr. Dvorak.
- Addition Beauty in symmetry.
- Anyway Old MacDonald had a farm...
- Tic-tac-toe Don't forget the horizontals.
- Modulus Lookahead smithwork.
- Matryoshka Pay attention to detail.
- Euclid Greed is good.
- Latin squares No mathematics; just logic and reasoning.
- Dominoes Caution! Rabbit holes.
Each problem has a robust solution (can be done "without cheating"), unlike "A man, a plan", "Glob", and "Balance" from the original set. In each case, the pattern should be unambiguous. A solution to a problem is considered robust if it conforms to this pattern for any string matching the problem's domain regex:
| Level | Domain regex |
|---|---|
| Subtraction | ^x+ - x+ = x+$ |
| Typist | ^[a-z]+$ |
| Addition | ^x+ \+ x+ = x+ \+ x+$ |
| Anyway | ^[a-z]+$ |
| Tic-tac-toe | ^[\.OX]{3} [\.OX]{3} [\.OX]{3}$ |
| Modulus | ^x+ % x+ = x+$ |
| Matryoshka | ^([a-z]+ )*[a-z]+$ |
| Euclid | ^gcd\(x+, x+\) = x+$ |
| Latin squares | ^[a-z]{4} [a-z]{4} [a-z]{4} [a-z]{4}$ |
| Dominoes | ^([0-6]{2} )*[0-6]{2}$ |
Please refrain from posting solutions here until the thread is well underway (20+ posts). Questions, total scores, and gentle hints are ok.
A warm thank you to Davidebyzero for helping me refine each of these problems, and for coming up with some brilliant solutions. Our testing and development notes can be found here and here (caution: spoilers).
I've been messing around with Matroyshka, and I can't come up with a definition of it that doesn't include several of the items on the "bad" list. All I can gather from the "good" list is that each successive word includes all the letters of the previous word, plus at least one more. But the "on", "sad", and "tea" bad lines also match that criteria, so I'm obviously wrong.