The Sphinx's Lair

Sphinx

01:31

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Many chess problems are dedicated to legal games, and very few to illegal ones. So I’ve decided to start another series of the latter! Every problem I make will have some offbeat thing about it that won’t follow normal chess rules. The position will provide you with plenty of clues as to what it...

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Q: Create a circle from right isosceles triangles

You have an infinite number of these right isosceles triangles, each consisting of three lines of equal width but no fill. You may scale each triangle to any size and the line width will remain the same. Construct a figure using as little triangles as you can, such that an intelligent human w...

visual triangle circle meaning human

Deusovi

02:53

@Sphinx opinion-based?

Rubio

03:04

@Deusovi Is that your opinion? ;)

Rubio

03:24

whew. I don't usually have to use two full comments up to almost entirely the last character to make my point, but this seemed worthwhile doing so.

Sphinx

04:12

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Q: 100 prisoners' names in boxes, against smart warden

My question, which I do not know the answer to, concerns the classic 100 prisoners and 100 boxes puzzle, summarized below. The solution to this assumes the names are placed in boxes randomly, and gets a ~30% probability of success. My question is what happens if the warden can choose how to pl...

mathematics strategy probability game-theory

Sphinx

08:27

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Q: The Brief Puzzle Hunt

Recently, I was invited to give a speech during the kickoff phase of a local puzzlehunt. I’ve almost finished writing my first draft, but I just can’t figure out the best way to end it off. Can you guys help me out? Here’s the draft: Welcome to the Brief Puzzle Hunt! Before we officially ki...

word enigmatic-puzzle knowledge story

humn

09:01

@Rubio , That's what i was going to say! Rand al'ias and i are only seen in the same room at the same time when space-time goes beyond warp.

@Randal'Thor , you! Me?! No, you. You have helped me along the path from rote technology to inspired expression. (Many a mile yet to go, of course. Oh here comes a YouTube, which i try to resist in this room:)

Many Rivers To Cross by Jimmy Cliff ~ Lyrics On Screen ~

►

(See you at The Troll, on a good day.)

. . .

Open question: I want to base a reverse-puzzling puzzle on a crossword puzzle in a public site that seems dormant but demands copyright permission. I sent a formal request that hasn't been replied. What to do?

Rubio

09:32

You Can't Always Get What You Want

►

humn

@Rubio , true, can't always get what we want. I was hoping to find a shortcut.

Rubio

Not sure there's one readily available for you on that one, sorry :)

humn

(And you Tubed as well, @Rubio. This is the wild west.)

Rubio

It seemed the only fitting way to answer you. Hehe

humn

But, somewhat seriously, seems we have to crossword ourselves to stay clear. This one's gonna net me another -245 points. +5 for a good question, -250 for bounties.

Bye, again, for now.

Chris Cudmore

13:28

@GarethMcCaughan However, in any bar I've been in, scotch is always a hand pour. The auto jiggers are used on the stock liquor, for mixed drinks.

Gareth McCaughan

13:46

I can well believe it, but I'm guessing the maker of the crossword didn't know that. (Or maybe some bars are different and they've been to ones where they use optics for the whisky.)

Chris Cudmore

Nah, I'm just a bar snob. I don't go out much, so when I do, it's high end places.

Sphinx

14:22

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Q: My Final thoughts

Problably a last try, good luck guys 252214 188812. 188812 22 614 26232268 26 2412146131823262322 2312 87262416 1161115181320. 1813212215181142213722 132612 8126 61426 142213722 2591815192613722 24121412 51224228, 22 11269262522138 1126926 26 1122881226 10622 24121382220186 23222418219269 ...

cryptography

Flog Edoc

16:52

Hey there guys.

So I've been meaning to double check on a logic puzzle I'm working about, but the sandbox on meta needs 5 rep.

Would it be alright to just post it and see how it goes? The main problem I want to identify is whether the logic part holds up mathematically and there's no accidental mistake somewhere.

John Dvorak

17:13

You could throw us a gist link. And - of course - making four edits is also an option :P

Sphinx

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Q: A story about liars

Evelyn, Skylar, Alayna, Madelyn, Jonathon, Lara, Alyin, Felix, Iris, Bob and Roslina live on an insland where some people always tell the truth, and the rest always lie. Roslina says "Alyin and Evelyn lie" Roslina says "Skylar would say 'Either Alayna lies, or At least one of Felix or Lara is t...

logical-deduction liars

John Dvorak

... or that

Flog Edoc

@JohnDvorak I've answered my own puzzle, don't know if that's alright here, but maybe a different style/method of answer than that could still be found.

John Dvorak

Usually you want to give other answerers some time and there's not much value in answering your own question on this site

Flog Edoc

Do I delete it then, the answer?

Gareth McCaughan

18:27

The usual procedure is to refrain from answering your own puzzles unless (1) a long time has elapsed and you've done all you can think of to help others solve it, or (2) others have solved it but you want to show your own approach because you think it has interest beyond the other solution(s).

Gareth McCaughan

18:43

@FlogEdoc I think your puzzle has no solution; that is, there is no assignment of truth-telling/lying to your characters that makes everything they say consistent with their nature.

1. I says F lies, so I says A&B both truthful, but I also says A lies, so I lies.
2. If A lies then F is truthful, so J is too, but J says A is truthful, contradiction; so A is truthful.
3. R says A lies, so R lies.
4. R says "either I lies or ..." which is true, so R tells the truth.

(But I make a lot of mistakes, so it wouldn't be a vast surprise if the above were wrong.)

Flog Edoc

19:01

@GarethMcCaughan There is in fact a solution, the one I deleted.

And it is a solution unlike what most would expect of a liar puzzle.

Gareth McCaughan

F says "Either A lies or B lies". It is, if they are all liars, true that either A or B lies. Therefore F is telling the truth.

Flog Edoc

No, double check your calculation.

Gareth McCaughan

OK, I double-checked it. What's wrong with it?

Flog Edoc

The puzzle was generated, not typed. Hence I'd be pretty sure of the answer I have, and it doesn't match yours.

Gareth McCaughan

So what is wrong with my reasoning?

Flog Edoc

19:14

Well, you can imagine a machine just spitting out the answer. Hence I am not familiar with the steps required to reach it, frankly, only that it is correct. And as far as the answer is, it isn't what you stated.

Gareth McCaughan

I can imagine a machine spitting out the answer, yes. I can also imagine a machine running buggy software. The reasoning above is not complicated; what do you think is wrong with it?

[note: AFK some of the time; apologies for any slow responses]

Flog Edoc

Well, if it's buggy, the best way to know would be equivalent to just solving it.

Gareth McCaughan

I have solved it. I arrived at the conclusion that there is no solution. Of course I could be wrong, but if so it should be pretty straightforward to find what's wrong with my reasoning. In particular, your answer claims that all the characters are liars and I gave a very short explanation of why the given statements seem to show that the characters are not all liars; do you think that reasoning is incorrect, and if so why?

Flog Edoc

There are 11 characters/people in the puzzle. It isn't solved that quickly.

Gareth McCaughan

19:29

What do you mean? It's solved as quickly as the time it takes to solve it. What, concretely, do you consider to be incorrect in what I've said above?

Flog Edoc

See the deleted answer

Gareth McCaughan

I've seen the deleted answer. It has a truth-table-looking thing whose exact meaning is not obvious, followed by a statement about who is lying and who isn't. It contains no actual reasoning. On its own it is no evidence of anything.

Flog Edoc

It's a truth table explaining the validity of each statement.

That having been worked out, it can then be concluded that the answer is as written

Are you saying the truth table is invalid?

Gareth McCaughan

I don't know whether it's valid because I still don't know what it means. You've got all the statements the characters made, and either TRUE or FALSE next to each one (but there's no indication of how those truth values were decided). And then you've said something about what characters are truth-tellers or liars (but it doesn't match the truth values in the right-hand column of the table, nor does substituting it in make the left-hand column match the right-hand column).

So it sure looks invalid, but perhaps I am misunderstanding what it's saying.

Flog Edoc

Here's an example: Say, "X claims B is a liar"

Then if I say it is false, it means X's claim is false.

In this particular case, it is much more complex, with "X claims that 'Either Y is a truth teller or Z'" etc

Gareth McCaughan

19:40

Sure. And whether X's claim is false depends on whether B is in fact a liar or not. So in order to get from the left-hand column of the truth table to the right-hand column, you need to assume particular truth-telling/lying dispositions for all the characters. There's no indication of what dispositions are being assumed. It certainly isn't the ones stated below the truth table.

Flog Edoc

You don't need to assume any disposition. If you calculate the (very) larger full-version truth table

You will be able to visualize it

All statements are logically connected to each other

Gareth McCaughan

I'm sorry, but you are not making much sense to me. It's possible that the problem is just that I'm being dim, but I don't think so. Let's please be very concrete, and look e.g. at the first row of the table. It says: "A and E lie", and "False". Where exactly does the "False" in the right-hand column of the first row come from?

Flog Edoc

Machine spat it out.

I don't know the details.

It is possible that there is a bug somewhere, but given that the solutions work for a lesser number of people, one would presume it is also the case when increased to 11 characters.

Gareth McCaughan

OK, let's start over. I am going to go through some reasoning, step by step. I would like you to consider each step -- they will be small steps -- and tell me when, if at all, you find something wrong in what I say.

Are you willing to do that?

(Also, a separate question. Did you program this machine that spat out the puzzle?)

Flog Edoc

I tested it out again with 11 characters, same result.

Gareth McCaughan

19:52

Are you willing to do what I described just above?

Flog Edoc

Your confusion might result from the recursive statements listed that contain three or more people mentioned, themselves within a quote that could be false. That is a major mind bender.

That some person X talks about another character Y, and this itself all being a quote from a third character Z

It gets pretty confusing

Gareth McCaughan

I think we may have a misunderstanding about the nature of this conversation.

I think you think I am having difficulty understanding the basics of how logic puzzles work.

I think you have posted what looks to me like an invalid logic puzzle, and are showing zero willingness either to consider that it might be invalid or to help me find where my reasoning is wrong.

I do not have difficulty understanding the basics of how logic puzzles work. I am a professional mathematician and (though it isn't my field) I have done post-grad stuff in mathematical logic. That doesn't at all mean I'm immune to making mistakes, and it could be that the error here is mine, but if so then what I need is concrete corrections rather than speculations about what sort of confusion I might be suffering.

Flog Edoc

What the issue is, I'm not exactly sure which particular phrase you are saying is wrong.

You're not saying the whole thing is wrong - which is what I might have initially presumed, only that some certain particular thing within the whole deal is mistaken

Gareth McCaughan

I have given some reasoning above that I think leads quite directly to the conclusion that the solution you posted is incorrect.

I am proposing to go through it step by step and see whether you see a mistake somewhere in it.

I am hoping that one of two things will happen. Either

1. you will spot a mistake in my reasoning, and then I can stop being unfairly patronizing at you and admit that maybe everything is OK. Or

2. you will accept that my reasoning is correct and that there is something wrong with the program that "spat out" the answer.

Flog Edoc

To be clear, I have no problem that the question (or the solution) are incorrect, only that I'm not sure in which part it is.

Gareth McCaughan

19:59

This seems to me like a reasonable procedure. You were asking above for some checking on your puzzle.

But so far you've responded to everything I've said with generalities, rather than showing any willingness to actually engage, and it's a bit frustrating.

Flog Edoc

I'm not sure how I can explain this further to you, other than gradually reducing the number of statements utilized in the puzzle to demonstrate that lower tiers are perfectly valid.

Gareth McCaughan

I am not asking you to explain anything to me.

Flog Edoc

Then there is nothing to clarify.

Gareth McCaughan

I am asking you to read some things I write and tell me whether you think they are wrong. I do not understand what problem you have with this.

Flog Edoc

I don't understand what you wrote.

It is jumbled up quite a bit.

Maybe you could clarify your intentions with it in a better formatted way.

Gareth McCaughan

20:03

Maybe I could. Let's see.

1. The alleged solution to your puzzle says that all the characters are liars. That is: A, B, etc., all lie whenever they say anything.

Anything wrong with that?

Flog Edoc

As far as I can tell, there doesn't seem to be, but I am open to being shown otherwise. I fully accept the fault being mine if there is ever enough evidence to said fact.

Gareth McCaughan

OK. Let's continue.

Actually, before we do, I think either I have misread something or there is a typo. Perhaps the former.

There's an Alyin and an Alayna. Is that a deliberate trap?

Flog Edoc

They're just normal names.

Gareth McCaughan

(Because I used A, B, etc., and didn't notice that...)

OK, so your two As are different, and indeed it looks like the error was mine. (Well, it might still turn out that the puzzle is broken, but the specific argument I made above is incorrect.)

They are not in any useful sense "normal names".

Flog Edoc

That is a linguistic argument, not a logical one.

Gareth McCaughan

20:08

And in a puzzle of this sort, having two characters whose names begin with the same initial seems like a deliberate attempt to trip solvers up.

Flog Edoc

Well, I won't say no if it does.

Gareth McCaughan

Oh, for sure. I'm not saying it's wrong. Just (1) disagreeing about them being "just normal names" and (2) suggesting that there's some trickery going on of a kind I happen to dislike. (Not just because I fell for it.)

Flog Edoc

It was not an intention exactly, but I guess now that you pointed out, it is indeed good evil trickery.

Gareth McCaughan

Anyway: I retract my claim that the puzzle is broken. I still don't understand what the truth table is supposed to mean, for the reasons I gave above, but of course it's possible that I'm just being dim there.

I need to do something else now. Apologies for the probably-false alarm.

Flog Edoc

The truth table lists the truth of every individual statement. It might seem as though every statement's own truth can be determined on its own, but that would be up to the solver to discover, because it may not be in fact the case.

If it ever turns out to be incorrect, I've got zero problems with that, I'll modify it or remove it.

Aha, I finally figured out the problem. The answers I was reading off were actually just like 'notes' to mark possible solutions, rather than any actual authoritative answer. It doesn't mean the question itself is wrong, only that the real answer may in fact not be the one I deleted after all.

I don't know if this advances anything, but I guess we shall wait for other answerers to post their attempts.

Rubio

20:39

Well now I'm confused. Is this your puzzle?

Flog Edoc

As in I made it, then nope.

Rubio

Eh.

You need to provide proper attribution for content that isn't your own

See here for more info. If this is from an online source, please provide a URL to the original. Regardless of where it came from, proper attribution is required, and noting the context in which the original appears is also recommended as in some cases (though perhaps not in this case) that added context can be of use to would-be solvers.

Gareth McCaughan

20:54

(Flog Edoc has added some attribution now. The page in question explicitly says to feel free to do what you like with the puzzles it generates, so I think that's OK.)

... Though, for the avoidance of doubt, we don't want a flood of machine-generated liars-and-truthtellers puzzles.

Rubio

I'm curious how much was "adapted" :)

Flog Edoc

It was originally a poem-based puzzle. When I realized the poem I made was fancy but the actual puzzle component I wasn't sure of, I thought, well, why don't I find the most evil way to make a liar puzzle there is?

And I ended up with 11 separate people/characters in one puzzle as you can see.

It would be doubly more evil with probabilities, but the question would be an absolute mess (and probably flawed somewhere)

Sphinx

23:06

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Q: The Librarian's labrynth

You've entered a library. The library is known for its large capacity, yet small size. Inside, you are in a room about the same size as the outside. There is one window on each wall (This is a four-sided building), except the side with the door which leads outside. You cannot see anyone inside or...

mystery

Alconja

23:43

C4 hint 1: the definition requires some creative interpretation (hence the '?')... which to use a Rubioism, is probably helpfulness level 0.

Hmm. On a hunch I just checked something, so I'm going to give an additional hint:

C4 hint 2: I've just discovered that one of the words in the clue is used in a primarily British sense...

Gareth McCaughan

@Alconja The solution to your CCCC is BARTENDER: R after TEND enthralled by BARE, and of course a bartender delivers (alcoholic) spirits to his customers.

(FWIW I'd already considered that exact parsing of the clue, though somehow knowing something is right rather than merely guessing it might be makes it much easier to follow through.)

Alconja

@GarethMcCaughan That's it.

Eric Tressler

That was my first thought on seeing the clue yesterday, and somehow I couldn't make it fit. I never got to "religious initiation = R" for some reason

Gareth McCaughan

Oh, that was almost my first thought. The thing I failed to think of was BARE.

CCCC: I follow "Religious initiation ..." clue, inevitably, symmetrically making first word used in a primarily British sense (9)

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