I told this riddle to an EE at my work recently and strangely he exploded angrily claiming that this riddle was a lie and impossible to solve or he would have solved it instantly. Yea, fat chance.
This riddle has no secrets or cheesy endings. No tricks, no mirrors, no one telling other islanders the answer. It can be solved completely through reasoned logic. So have at it...
On an island are 201 people. 100 of them have blue eyes. 100 of them have brown eyes. 1, the "leader" as it were, has green eyes. No one knows the color of their own eyes but of course they do know the color of everyone else eyes. For all they know, their eyes could be red. No one can tell an islander his/her eye color.
These people are trapped on the island until they can deduce their own eye color. Everyday, a ship comes by to pick up anyone and everyone who has figured out his/her eye color.
They are all perfect logicians and it can be said that if it could be figured out through logic it will be instantly deduced and therefore you can count on the islanders to act in the most advantageous way (that is, the way most likely to get them off the island).
Exactly 1 time in their entire existence, the leader may say something to the crowd. One day she stands before them and without looking at anyone in particular says, "I see someone with blue eyes."
The question then is who gets to leave the island and when do they get to leave? There are other interesting questions to answer like to specifically note what about the statement provides enough information for someone to escape?
Ok like I said, there are no tricks, no sign language, no showing up on the boat to see if you get kicked off. I'll leave this up here for a few weeks before posting some multiple choice answers as a vote. If you know the answer or figure it out, comment your answer but don't include your reasoning. It's an interesting puzzle in that the same kind of logic you use to proof this riddle forms the foundation of a type of computation called recursion that is fundamental to my discipline.
Ross
Wednesday, September 26, 2007
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4 comments:
it seems you've left all of thesharester's blog-readers dumbfounded. i, however, am neither ashamed nor angry to admit that i have no clue. anxiously awaiting multiple choice...when given options, i'm the best guesser i know. :-)
ooohh!! i love this :)
Ok, my answer is everyone will figure out their eye color and will all go home on the boat (provided they all fit of course ;)
Ross, can you post your email so we can send our logic and you can tell us if we're right???
oh... and on my logic, they all leave the island on that night.
r.hytnen@gmail.com
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