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The Hardest Logic Puzzles

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Re: The Hardest Logic Puzzles

#12

#2 is easy, by using double negatives and asking the same question to each god (asking different questions does you no good): "Is the other non-random god capable of lying?" The truth telling god will always answer: "yes" (da || ja) The false telling god will always answer: "yes" (da || ja) [the truthful answer is 'no', but this god tells only lies, therefore the answer is 'yes'] The random god will answer: "yes || n…

How can you then distinguish between the two non-randomly-answering gods? They will answer the same, and the answer from the randomly-answering god appears to contain no useful information.

Oh, I must not have read the instructions thoroughly enough - I thought the solution was looking for an answer, not for the identities. My bad.

I'm guessing the same principle should apply though, I'll comment an update if I don't fall asleep from having been up all night. Thanks for pointing that out, though.

Re: The Hardest Logic Puzzles

#13
What makes a difficult sudoku problem difficult?

Is it possible that a brilliant, experienced solver would find the right "tricks" to solve the puzzle? Or is the sudoku such that it can be only solved by some flavor of exhaustive search on the space of potential solutions?

Re: The Hardest Logic Puzzles

#14

#2 is easy, by using double negatives and asking the same question to each god (asking different questions does you no good): "Is the other non-random god capable of lying?" The truth telling god will always answer: "yes" (da || ja) The false telling god will always answer: "yes" (da || ja) [the truthful answer is 'no', but this god tells only lies, therefore the answer is 'yes'] The random god will answer: "yes || n…

Please, if you're going to give a solution, rot13 it or link to it or something. Don't blurt it out in the first line of your answer.

Re: The Hardest Logic Puzzles

#15

What makes a difficult sudoku problem difficult? Is it possible that a brilliant, experienced solver would find the right "tricks" to solve the puzzle? Or is the sudoku such that it can be only solved by some flavor of exhaustive search on the space of potential solutions?

The difference between an "easy" and a "hard" sudoku (and other problems of that ilk) is essentially how many steps ahead you need to think in order to derive useful information.

An "easy" sudoku is one solvable by mechanical application of the rules of the game - if there's only number that can be placed in a cell, fill it in, and similarly if there's only one cell in a given row, column, or box that a given number fits in, fill it in there.

As things get harder, other logical steps are required. For example, if there are two cells in a line, and both of them can only accept the numbers 5 and 9, you can conclusively say that no other cell in that line can be a 5 or a 9. That's looking one step ahead, and (depending on how often it's necessary) makes for a medium-difficulty puzzle.

As you move up difficulties things get more complex, and thinking several steps ahead becomes necessary if you want to make meaningful headway.

--

I would expect the "hardest" sudoku would not be one that's only solvable by brute force - that's a rather uninteresting puzzle, for a start. Instead, the hardest (in my opinion) would be one that requires making the trickiest insights in order to make headway without resorting to guess-and-check style exhaustive search.

Re: The Hardest Logic Puzzles

#16

#2 is easy, by using double negatives and asking the same question to each god (asking different questions does you no good): "Is the other non-random god capable of lying?" The truth telling god will always answer: "yes" (da || ja) The false telling god will always answer: "yes" (da || ja) [the truthful answer is 'no', but this god tells only lies, therefore the answer is 'yes'] The random god will answer: "yes || n…

How can you then distinguish between the two non-randomly-answering gods? They will answer the same, and the answer from the randomly-answering god appears to contain no useful information.

So I started to work it out, only to discover the link about the problem in the article gives it away - counterfactuals can be used, so might as well read that instead of any thing I come up with. And thus I just wasted a bunch of time trying to figure out which specific one worked (now erased) ... but my hunch was correct! (Although hunches are hardly proofs, tsk tsk)

Also, I want to thank you again for helping me out with awk/sed/grep/command line stuff, from a year ago!

Re: The Hardest Logic Puzzles

#17

Earlier quoted context omitted.

How can you then distinguish between the two non-randomly-answering gods? They will answer the same, and the answer from the randomly-answering god appears to contain no useful information.

So I started to work it out, only to discover the link about the problem in the article gives it away - counterfactuals can be used, so might as well read that instead of any thing I come up with. And thus I just wasted a bunch of time trying to figure out which specific one worked (now erased) ... but my hunch was correct! (Although hunches are hardly proofs, tsk tsk) Also, I want to thank you again for helping me o…

You're welcome!

Re: The Hardest Logic Puzzles

#18

#2 is easy, by using double negatives and asking the same question to each god (asking different questions does you no good): "Is the other non-random god capable of lying?" The truth telling god will always answer: "yes" (da || ja) The false telling god will always answer: "yes" (da || ja) [the truthful answer is 'no', but this god tells only lies, therefore the answer is 'yes'] The random god will answer: "yes || n…

vg vf cbffvoyr gb qrgrezvar gur vqragvgvrf bs gur guerr tbqf jvgubhg xabjvat juvpu jnl ebhaq wn naq qn ner. (r.t. guvax nobhg ubj gb qb guvf jvgu whfg gur Gehr naq Snyfr tbqf, vtabevat Enaqbz)

gur dhrfgvbaf lbh ner nfxvat va trareny fubhyq punatr qrcraqvat ba gur bofreirq qn|wn nafjref gb gur cerivbhf dhrfgvbaf. n fgengrtl pna or n gerr bs dhrfgvbaf, abg n frdhrapr svkrq va nqinapr.

gur uneq ovg vf vfbyngvat gur enaqbz tbq sebz gur bgure gjb tbqf. abgr gung gur enaqbz tbq qbrf abg enaqbzyl rzvg lrf be ab (rapbqrq nf wnqn), vg enaqbzyl nafjref gur tvira dhrfgvba rvgure gehgushyyl be snyfryl. fb lbh pna senzr n fhvgnoyl pbagbegrq dhrfgvba gung sbeprf gur fnzr erfcbafr sebz gur enaqbz tbq va obgu gehgul-zbqr naq snyfrl-zbqr, gung qvfgvathvfurf vg sebz gur aba-enaqbz tbqf...

Re: The Hardest Logic Puzzles

#19
post #18

#2 is easy, by using double negatives and asking the same question to each god (asking different questions does you no good): "Is the other non-random god capable of lying?" The truth telling god will always answer: "yes" (da || ja) The false telling god will always answer: "yes" (da || ja) [the truthful answer is 'no', but this god tells only lies, therefore the answer is 'yes'] The random god will answer: "yes || n…

vg vf cbffvoyr gb qrgrezvar gur vqragvgvrf bs gur guerr tbqf jvgubhg xabjvat juvpu jnl ebhaq wn naq qn ner. (r.t. guvax nobhg ubj gb qb guvf jvgu whfg gur Gehr naq Snyfr tbqf, vtabevat Enaqbz) gur dhrfgvbaf lbh ner nfxvat va trareny fubhyq punatr qrcraqvat ba gur bofreirq qn|wn nafjref gb gur cerivbhf dhrfgvbaf. n fgengrtl pna or n gerr bs dhrfgvbaf, abg n frdhrapr svkrq va nqinapr. gur uneq ovg vf vfbyngvat gur enaq…

Apropos of nothing in particular ...

Not bothering to use ROT13, I just dropped that into my generic substitution cipher decoder and it spat out the answer almost immediately - quite pleased with that.

Re: The Hardest Logic Puzzles

#20
post #18

Earlier quoted context omitted.

vg vf cbffvoyr gb qrgrezvar gur vqragvgvrf bs gur guerr tbqf jvgubhg xabjvat juvpu jnl ebhaq wn naq qn ner. (r.t. guvax nobhg ubj gb qb guvf jvgu whfg gur Gehr naq Snyfr tbqf, vtabevat Enaqbz) gur dhrfgvbaf lbh ner nfxvat va trareny fubhyq punatr qrcraqvat ba gur bofreirq qn|wn nafjref gb gur cerivbhf dhrfgvbaf. n fgengrtl pna or n gerr bs dhrfgvbaf, abg n frdhrapr svkrq va nqinapr. gur uneq ovg vf vfbyngvat gur enaq…

Apropos of nothing in particular ... Not bothering to use ROT13, I just dropped that into my generic substitution cipher decoder and it spat out the answer almost immediately - quite pleased with that.

Interesting. You cycle through substitutions and match against a dictionary to detect a hit?
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