- 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).
Welcome! :)
Yes, the difficulty in this one is more to do with pinning down the precise pattern than in building the regex or in compressing it. Focus on the "on" and "sad" lines in particular.
Good luck!