Reply
Thu 19 Aug, 2004 10:33 pm
You need to know the answer to a yes/no
question, and as luck would have it you
are in a room with three people who know
the anwer to the question. Unfortunately,
one of them always lies, one always tells
the truth, and one lies or tells the truth
at his whim.
Can you determine the answer to your
question by asking only two yes/no
questions total.
Notes:
1. They know who the truthteller, liar,
and random guy are.
2. Each question you ask only is answered
by the one person you directed it to.
Call the question you're trying to answer Q.
First find one person who is not the random guy.
Call them A, B, and C. Ask A, "Is B more truthful than C?" If the answer is yes, then C is not the random guy. If the answer is no, then B is not the random guy. This can be verified by examining all possible permutations. Note that you don't know the identity of anyone at this point. You've only identified one who is not the random guy.
Ask this non-random guy (B or C from above), "How would the the other non-random guy answer question Q?"
The answer to Q is the opposite of the answer you receive.
Stumble It!
Tweet This
Bookmark on Delicious
Share on Facebook
Share on MySpace