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propensive's profile
Jon Pretty
Jon Pretty
Jon Pretty
@propensive

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Jon Pretty

@propensive

Supporting Scala through professional training and open-source software. Responsible for Magnolia, Fury, Scala World and Functional Africa.

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propensive.com
Joined July 2010

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    1. Jon Pretty‏ @propensive 29 Sep 2019

      There are 100 prisoners, numbered 1-100. The prisoners' numbers are written onto 100 cards, put randomly into 100 envelopes numbered 1-100. They can't communicate, but are invited, one by one, to open 50 envelopes. If any prisoner fails to find his number, they all get killed.

      9 replies 13 retweets 55 likes
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    2. Jon Pretty‏ @propensive 29 Sep 2019

      At best, there's a 50% chance any one prisoner can find his number. It would seem like there's a probability of (½)¹⁰⁰ or 0.00000000000000000000000000008% that every prisoner could find his own number, if each were to check 50 envelopes at random.

      2 replies 0 retweets 1 like
      Show this thread
    3. John‏ @chautelly 29 Sep 2019
      Replying to @propensive

      So, if it were 2 prisoners opening 1 envelope I would tell them to start with envelope with the same number as their position in line

      1 reply 0 retweets 1 like
      Jon Pretty‏ @propensive 29 Sep 2019
      Replying to @chautelly

      That (or the isomorphic strategy) would be the perfect strategy for two prisoners, and they would have a 50% chance of survival.

      8:09 AM - 29 Sep 2019 from Krakow, Poland
      1 reply 0 retweets 0 likes
        1. New conversation
        1. Jon Pretty‏ @propensive 29 Sep 2019
          Replying to @propensive @chautelly

          What about four prisoners opening two envelopes?

          2 replies 0 retweets 0 likes
        2. John‏ @chautelly 29 Sep 2019
          Replying to @propensive

          Work toward the middle? So prisonor 1 opens 1 and 4?

          0 replies 0 retweets 0 likes
          3. End of conversation

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