You are lost once again in the land of Knights, Knaves, and Liars, and once again you find yourself at a fork in the road. You know that one path will lead you to a safe return home, while the other will lead you to your own gruesome demise. (You really need to find a better vacation spot next year!)

Standing at the fork is a native, who might be either a Knight (who always tells the truth), a Knave (who alternates between true and false statements), or a Liar (who always lies). You have no way of knowing which he is. Worse yet, you realize that if he is a knave, you don't know if he will tell you the truth first, and then lie, or lie first and then tell the truth, etc.

What is the fewest number of questions you have to ask to find out which is the safe road, and what are they?

(In reply to My solution by Caleb)

Two thoughts.
1. What if the native considers that the "right" way is the way that leads you to a gruesome demise. ie the native is not friendly and your demise is the outcome that is preferred. Perhaps asking about "safe" rather than "right" will overcome this.

2. If the native is a Liar and considering a complex question, does he lie to himself when deciding each part and then lie when giving the final result. Thus lying to himself when asking "is this the right/wrong road; or when deciding if he/she is a Knight/Knave or Liar.

Above thoughts first raised by Martin Gardner (of Scientific/Mathematicals Puzzles fame) - he also suggested the "beer" solution I proposed in an earlier post.

Posted by Vernon Lewis on 2006-05-23 07:17:33