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The blue eye problem

Discussion in 'Off-Topic' started by Merick, Oct 12, 2006.

  1. Merick

    Merick IncGamers Member

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    The blue eye problem

    Apparently it's supposed to be a really hard and not cheap logic problem.
    I really don't have any idea, anyone want to give it a shot?

    http://xkcd.com/blue_eyes.html

     
  2. {KOW}Spazed

    {KOW}Spazed Banned

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    EDIT: Link was slightly different in the information that the islanders had, which made this whole thing pointless.

    I don't understand it completely, but it seems to work out nicely.
     
  3. Merick

    Merick IncGamers Member

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    This has nothing to do with volcanoes. Are you sure this is the same problem?
     
  4. {KOW}Spazed

    {KOW}Spazed Banned

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    If blue eyed people = 1 then he leaves the night the Guru tells them.

    If blue eyed people = 2 then seeing that only one other blue eyed person is there and that no one left the previous night will leave.

    That goes on forever so the answer is the amount of blue eyed people minus one days.

    At least that is how I think it should work. My link confused the hell out of me and I think I am actually going against what it says. The link told the islanders that there was at least one blue eyed person, so the guru actually wouldn't be disclosing any information and all the blue eyed people would have already left. It was a faulty version of the riddle.
     
  5. Xynrx

    Xynrx IncGamers Member

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    Hey, that's a really slick problem. I like it.

    The solution involving volcanoes and people leaving on ships are very similar. Here's the jist of why:

    Basically, the mathematical induction from the volcano link says that since everyone is a master logician, they will all know what the only solution is.

    Now, with that said, here is the answer to the two similar but different problems:


    Volcano:
    - Blue eyed people must die.
    - If you have BROWN eyes you see X number of people with blue eyes.
    - If you have BLUE eyes you see X-1 number of people with blue eyes.
    - the magical logic that everyone is expected to understand without discussion is that everyone with blue eyes jumps into the volcano when the number of days past equals the number of blue eyed people... that's it

    Here are the two scenarios assuming there are 4 blue eyed people (X=4)
    i) You have blue eyes, and you see 3 blue eyes. If they all kill themselves on day 3 you have brown eyes, if they don't, logically, you must also have blue eyes. You die on day 4.

    ii) You have brown eyes, and you see 4 blue eyes. The blue eyed people go through the same logic as you did in part i). They only saw 3 people with BLUE, and you saw 4. They all kill themselves for the same reason as in part i) and you therefore must have brown eyes.



    Ships:
    - everyone must know their eye colour before leaving
    - the same magical logic occurs as above with the exception that everyone questions whether or not they have that 100th blue eyes or 101st brown eyes, or vice versa brown/blue
    - all blue see 99 blue and 100 brown, and all brown see 100 blue and 99 brown
    - same deal, if you are blue, and think you may be the 101 brown, you assume each blue only sees 98 other blues plus themselves, thus they all leave on night 99. vice versa with brown/blue
    - since no one will leave on night 99 since they see AT LEAST 99 of blue and 99 of brown (plus one), they have to wait one more day because no one had boarded and thus all leave on night 100.
     
  6. Dondrei

    Dondrei IncGamers Member

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    That didn't make any sense.

    That is a very confusing sentence.
     
  7. Cannon Fodder

    Cannon Fodder IncGamers Member

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    Man I see this one pop up more and more- first ran into it about 4 years ago. Stumped me for a good 15 minutes before I got it the first time.
     
  8. UserMathias

    UserMathias IncGamers Member

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    Not sure I get it. If the assumption is that

    and no one else, then there can't be a red-eyed person, or less than 100 blue-eyed people and so on.
     
  9. {KOW}Spazed

    {KOW}Spazed Banned

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    The people don't know that, they only know what is in the first paragraph and the one thing the Guru said.

    That is why I took my link down, it gave them that information. . .so no need for the Guru.
     
  10. Dondrei

    Dondrei IncGamers Member

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    I don't get it at all. The idea of induction is impossible, no-one knows their eye colour until people start leaving, and no-one can leave until they know their eye colour. So no-one leaves in that case.
     
  11. Johnny

    Johnny Banned

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    The funny part is someone probably spent days and countless effort making that up and the best it can do is raise a few eyebrows and then people lose interest.


    Then in 15 min someone poops out a ytmnd thats 100 times as amusing.
     
  12. Dondrei

    Dondrei IncGamers Member

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    Ah, the classic.
     
  13. nosignal

    nosignal IncGamers Member

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    Just scale the numbers down to three a side or something. It'll be easier to figure out, I guess.
     
  14. ffejrxx

    ffejrxx IncGamers Member

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    everyone should be able to figure it out by the second day if the people dont know how many people on the island have the same eye color (it would have been easier if they said there was a random population of blue and green eyed people totaling 200)

    everyone except the guru should be gone by the second night

    the first night everyone could guess and those that guessed correctly would leave

    at noon the second day the guru would say "I can see someone who has blue eyes." unless everyone with blue eyes guessed correctly

    the second night everyone left could change their answer to the correct one
    the only ones left after the second night would not have green or blue eyes
     
  15. {KOW}Spazed

    {KOW}Spazed Banned

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    Guessing doesn't count, they have to use logic to figure out their eye color.
     
  16. Johnny

    Johnny Banned

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    On the 2nd day I arrive in a speed boat with a dagger then just for the fun of it shank all 200 of them. Because none of the unarmed blind and deaf people could figure out a logic way to defend themselves they all die and then I take the foxy green eyed guru babe with me in the speed boat back home. And after that all she ever saw was my blue eyes... And stars ofcourse.
     
  17. caddad

    caddad IncGamers Member

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  18. ffejrxx

    ffejrxx IncGamers Member

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    then they would all figure have it out the first night since there so logical
     
  19. {KOW}Spazed

    {KOW}Spazed Banned

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  20. {KOW}Spazed

    {KOW}Spazed Banned

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    No, it takes time for the information to get out.
     

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