5 ms·

Ask what would the other do and do the opposite.

• m463 2y ago
  I wonder if you could do that with tristate logic somehow. maybe with more guards or other variables.
  • flir 2y ago
    Solve for the general case. Maybe you need num_guards-1 questions? I doubt you could solve for 50 guards with 1 question.
    • judahmeek 2y ago
      If you're allowed to create a hypothetical question that translates a hierarchy of guards into Boolean logic, then it doesn't matter how many guards there are.
      • flir 2y ago
        What are you thinking? I was wondering about dividing them into sets.
        • saghm 2y ago
          "What would each of the other 49 guards would say the 49 guards other than them would do?" It would be a pain to do the deduction from all of that info, but it seems like it would be enough enough. Maybe it would make more sense to have that guard write down the answer (and throw in a pencil and a few extra sheets of paper)...
          • flir 2y ago
            "Label the guards, 1 to 50, starting with you as 1, the guard to your left as 2, etc. For each guard, tell me what answer they would give if I asked them if your door was safe". If all the guards say the same thing, you're talking to the lying guard. Otherwise the liar is simply the one that answers differently. Would that work? I think so.