You're trapped in a room with 2 doors, one on your left and one on your right. One door leads to heaven, one door leads to hell. There are two birds in the room. One is a bad bird, which always lies, one is a good bird, which always tells the truth. You don't know which door is which, nor do you know which bird is which. The birds know which door is which.
You get to ask one question to one bird. How do you figure out which door leads to heaven?
This puzzle has some typical "expansions" to make it more difficult, like
You may not ask about the other bird
or equivalently (I think?)
There is only one bird which either always tells the truth or always lies.
From this expansion on, there is a post often going around online, considered a "troll post" (http://i.imgur.com/huBYtN5.jpg), which adds the following:
You may not use IF statements or any hypothetical statements in your question
I believe adding the restriction that forces a question to have a reply of either "true" or "false" does not change the difficulty, so let's work with that.
A solution I came up with the help from a stranger online, was asking the following question: "(Does the door on the left lead to heaven) XOR (Do you always speak the truth)"
My doubts about this are:
1) Is XOR not a hypothetical statement?
2) Would a lying bird lie about the entire question, or about the subquestions that are being XOR'd, or about all? (This may just be "definition"?)