Knights & Knaves - A logic puzzle (poll included)

Turtle on 10/10/2008 at 15:56

You know you could always leave your

Gambit on 10/10/2008 at 16:39

A puzzle generator ?
That sounds so cool. Where did you find it ?

And this puzzle reminds me of that "Labirinth" film.

Turtle on 10/10/2008 at 16:43

browser window open and finish your thought when you're ready.

io organic industrialism on 10/10/2008 at 17:32

Quote Posted by Gambit

A puzzle generator ?
That sounds so cool. Where did you find it ?

And this puzzle reminds me of that "Labirinth" film.

Here is the site I stumbled across originally yesterday

(http://www.hku.hk/cgi-bin/philodep/knight/puzzle)

Apparently the university of Hong kong never actually got permission from Zac Ernst to use them for their site.. but he doesn't care. Anyway Zac generated the puzzles a long time ago and has since lost the program he wrote to do it.
This other person made a program to interperet the grammar in his puzzles and "solve them" (sometimes incorrectly as we now know)
(https://twiki.soe.ucsc.edu/twiki/bin/view/SoeClasses/AIClassKnightsKnaves)

demagogue on 10/10/2008 at 17:42

It looks like the algorithm went down the path that checked the condition Sally as knight and Zippy as knave and that checked clear, so it either stopped there (for optimizing reasons) or it picked it out of a number that checked clear (for some other optimizing reason).

Sally's sentence is easy to clear because "not the same" translates directly to "f(Sally) != f(Zippy)", which is straight-forward to check as true.

For Zippy, hmm, I had a reason why it got it wrong, but I need to think a little more because I'm not sure that works either... I think it has to do with mistranslating the logic of "exactly one" so that it checks it against both Sally and Zippy being knights (since it doesn't specify which one is "exactly" a knight), and since the condition is Zippy is a knave, that's not a knight, so the logic clears. But I have to double check to see how that works out, where the mistranslation comes from.

Edit: By the way, I should add that I really like the logic that goes into computer parsing and answering questions, and have tried my hand at a few similar sorts of programs. Sort of a weird hobby I guess. It gets very complex very fast, not so much the logic itself, but making sure the natural language gets translated to the right logic.

Gambit on 10/10/2008 at 18:02

By the way, I know a cool one...

There´s a special island (copyright included) where a tribe took you as a prisoner.
Now you are going to be submitted to a test.
You must make a statement. (Ex: "The sky is blue.")
The judges of the tribe are omniscient and know about everything.

If they know that your statement is true (and they really know everything, since they´re omniscient) then you will be sentenced to drow in the water.

If they know your statement is false (and you won´t fool them, omniscient, blah blah blah...) then you will be sentenced to burn on fire.

Time to say your statement. How will you scape death ?

Matthew on 10/10/2008 at 18:04

I always lie?

Gambit on 10/10/2008 at 18:08

Quote Posted by Matthew

I always lie?

The omniscient judges know everything. Including your past life. They know you don´t always lie, that you have made true statements before.
So this specific statement is a lie and you are now burning on fire.

Kolya on 10/10/2008 at 18:22

They can't kill me. Ideas are bullet proof.

N'Al on 10/10/2008 at 18:32

Quote Posted by Gambit

"I will die by burning on fire."