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The New Coffee Room

  1. TNCR
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  3. Puzzle time - prisoners and hats

Puzzle time - prisoners and hats

Scheduled Pinned Locked Moved General Discussion
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  • KlausK Offline
    KlausK Offline
    Klaus
    wrote on last edited by
    #8

    I think I now remember where I saw the puzzle.

    There's a mathematician who publishes such puzzles on a regular basis, Peter Winkler. He has a monthly column in the "Communications of the ACM", of which I'm a subscriber. I believe I saw that puzzle there. If I think about the puzzle more, I may remember parts of the solution, so I guess I better just keep my mouth shut.

    1 Reply Last reply
    • HoraceH Offline
      HoraceH Offline
      Horace
      wrote on last edited by
      #9

      I guess the set of rules would attempt to clump wrong guesses together while right guesses would tend to be alone. The rules would also want to ensure that at least one person guessed.

      Education is extremely important.

      HoraceH 1 Reply Last reply
      • MikM Offline
        MikM Offline
        Mik
        wrote on last edited by
        #10

        If they were that smart they wouldn't be prisoners, now would they?

        “I am fond of pigs. Dogs look up to us. Cats look down on us. Pigs treat us as equals.” ~Winston S. Churchill

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        • HoraceH Offline
          HoraceH Offline
          Horace
          wrote on last edited by
          #11

          Tell that to Stalin and his pogroms against intellectuals.

          Education is extremely important.

          1 Reply Last reply
          • HoraceH Horace

            I guess the set of rules would attempt to clump wrong guesses together while right guesses would tend to be alone. The rules would also want to ensure that at least one person guessed.

            HoraceH Offline
            HoraceH Offline
            Horace
            wrote on last edited by
            #12

            @Horace said in Puzzle time - prisoners and hats:

            I guess the set of rules would attempt to clump wrong guesses together while right guesses would tend to be alone. The rules would also want to ensure that at least one person guessed.

            So, is the answer that simple? Those who see two different colors would not vote. If the other two people are same, guess opposite? This will cause any configuration of colors other than all-same to be a win (one correct vote), while all-same would be a loss (3 wrong votes).

            Education is extremely important.

            1 Reply Last reply
            • KlausK Offline
              KlausK Offline
              Klaus
              wrote on last edited by
              #13
              1. Do the prisoners know (or can determine) the order in which they are asked?
              2. Can the prisoners hear all the answers?
              1 Reply Last reply
              • KlausK Offline
                KlausK Offline
                Klaus
                wrote on last edited by
                #14

                Oh, I think I now remember the key to the solution. The probability can be raised to 75%.

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                • HoraceH Offline
                  HoraceH Offline
                  Horace
                  wrote on last edited by Horace
                  #15

                  Yes that is the % of my proposed solution. I got there by figuring that each guess would be 50/50 so the rules would have to clump wrong guesses together and single out right ones. One such set of rules leaves 75% of color combinations yielding one right guess.

                  Education is extremely important.

                  1 Reply Last reply
                  • jon-nycJ Online
                    jon-nycJ Online
                    jon-nyc
                    wrote on last edited by
                    #16

                    I got the same answer as Horace.

                    Official answer comes out Saturday but I cant see them improving on 75%.

                    Only non-witches get due process.

                    • Cotton Mather, Salem Massachusetts, 1692
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                    • KlausK Offline
                      KlausK Offline
                      Klaus
                      wrote on last edited by
                      #17

                      It gets interesting if you generalize the number of prisoners and/or the number of colors.

                      https://arxiv.org/abs/cs/0509045

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                      • jon-nycJ Online
                        jon-nycJ Online
                        jon-nyc
                        wrote on last edited by
                        #18

                        Oh man, you ruined the bonus round. 😉

                        Only non-witches get due process.

                        • Cotton Mather, Salem Massachusetts, 1692
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