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This reminds me of another similar puzzle. This one is much easier, I think.
The king buries 4 prisoners up to their necks, 3 on one side of a wall, and one on the other. Each faces the wall. He puts a hat on each, as shown. Each can see the hats in front of him, but can't see through the wall:
He says, "There are 2 black hats and 2 white hats among the 4 of you. You will all go free if one of you can tell me which color you are wearing. Otherwise, you will all be executed. No communication is permitted. You have one minute. Begin."
What happens?
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the guy in back doesn't say anything, which tells the second guy that he doesn't know, which means that he and the first guy are wearing different colored hats.