ou are a logician in training for the police, and the time has come to take the certification test. The police chief brings you the test one morning, and says, "I must warn you, this is your only chance at the certification test; If you fail, you must keep training for another year before you can take it again."
           
- Five suspects were interrogated for a bank robbery.
             
- Each suspect was either a knight, a knave, or a liar.
         
- Knights always tell the truth.
       
- Liars always lie.
       
- Knaves strictly alternate truths and lies with each statement.
                   
- Police have evidence that suggests the perpetrator acted alone.
                   
- Police have evidence that suggests the perpetrator acted alone.

>During the interrogation, two questions were asked (consecutively) of each of the five suspects. Each suspect heard the other suspects' responses, and none of them made a statement between his or her two answers. Here are the two questions and their responses.

"Did you rob the bank?"
A: No.
B: No.
C: No.
D: Yes.
E: Yes.

"Who robbed the bank?"
A: E.
B: A.
C: l don't know.
D: E.
E: A.

The interrogators mentioned that something about their statements didn't seem quite right. The police chief adds, "The only hints I can give you are that C is not a knight and that there is only one correct answer. I'll be back in 24 hours to ask you who robbed the bank."

(In reply to Possible - with inspiration from others... by Kenny M)

Maybe I'm missing something, but I don't see how that's any different from what I and others have already said.  No offense, I just think I'm going a little batty with this one.  We're all going in circles here, I know I personally am driving myself nuts over it.

I don't even know where to start anymore, I'm exploring possibilities ranging from the somewhat improbable (the chief is the thief) to the completely ridiculous (one or more of the suspects speak Spanish...don't ask) and I don't feel like I'm anywhere near the heart of the problem.

From what I can gather, it can't be a mistake that this is in the "Cryptography" category - that doesn't seem like the kind of error that would go unnoticed at this site.  Combined with the fact that "something about their statements didn't seem quite right" and the lowercase "L" in C's second response (which would seem to be an extremely unlikely typo considering its placement on the keyboard and the otherwise meticulous spelling and grammar of the problem), there has to be something about those letters we are all not seeing.

Assuming the solution does not turn out to be a huge disappointment, kudos Dustin for a great puzzle!

 

Posted by tomarken on 2006-03-02 19:20:13