You are trapped in a dungeon, and see two doors in front of you. One is a way out, andther will lead to certain death.
Two people are standing in front of these doors, one of them a Knight, another - a Liar. Naturally, you do not know who is who, but they know each other's true nature.
Both the people know which way is correct, but you can only ask one question of one of them before making your choice.
What will you ask?
Given only one question that an individual can ask of an individual who may be either a truthteller or a liar and get the correct answer directly (i.e. without having to take the opposite action) would be the following. "If I were to ask you if this is the right direction, would your answer to that question be the same as it would be to "Are you a truthteller?" Assume the direction is wrong. The truthteller would answer No to the first question, Yes to the second, and No to the third. The liar would answer Yes to the first questions, No to the second and No to the third. Thus both give a "No" response. If the direction is correct, the truthteller answers Yes, Yes and Yes and the liar No, Yes and Yes. In each case, the final answer provides the correct guidance. Gordon S.
An Alternative Dungeon Problem Solution
