"The world's most difficult logic puzzle!"

[jack]

"The world's most difficult logic puzzle!"

"As you are walking along a road you come to a cross-roads, at which stand three inhabitants of the island who are unfamiliar with boolean logic and double negatives. One of them..."

:)

(That's a reference to a Raymond Smullyan puzzle that several people have linked to recently, with three gods, who speak an unknown language, and answer truthfully, falsely, or unpredictably, and you have to work out which is which with yes-no questions. I think now I remember enough similar puzzles to know how to do it. Except that I'm sure I remember discussing a specific instance -- probably very similar except for the language irrelevant complication -- on livejournal, probably with simont, but I can't find that discussion now.)

Comments

[woodpijn.livejournal.com]

...and I've solved the full da/ya version. Yay.

I disagree that it's the hardest one in the world. The hardest one I've encountered is something to do with 100 prisoners opening 100 boxes one at a time in a room, without conferring. I can't remember the precise details, but when I first encountered it it seemed completely out of the realm of possibility, rather than "oo, if I just had one more question / one more weighing / one fewer ball, I could do it". I got the answer eventually, with quite a bit of help, and still find it awe-inspiring.

[woodpijn.livejournal.com]

...and I've solved the full da/ya version. Yay.

Actually I'm not sure if I have, doh. The da/ya version is indeed a trivial generalisation of the English version, but I'm not sure if my solution to the English version was correct after all (or if it was correct and I now can't remember it, which is even more frustrating).

[cartesiandaemon.livejournal.com]

I disagree that it's the hardest one in the world.

Yeah, I think you're right. I think if you're unfamiliar with the genre, having the three gods AND the obscuring language is very intimidating, and you'll get bogged down in details. But I remember the 100 prisoners one too, and I don't think I ever *did* work it out.

For that matter, I think Smullyan wrote a book encoding Godel's incompleteness theorem in liars-and-truth-tellers problems, which has to win some sort of award for insane, but I don't think can really count as either single, nor puzzle.

Maybe there's some category like "hardest problem which is simple once you see it" or similar?