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Rune <aut### [at] runevision com> wrote:
> There are two passages of which you must choose one. One of them leads to
> freedom, the other one to doom. Once you have chosen one, you are stuck with
> it. In front of each passage is a guards. One guard always tell the truth
> and one always lies. You don't know which does what. Now you must find out
> which passage to choose by asking the guards questions...
The vast majority of people pose the problem like that, and they all get
it wrong. That's because that is not limiting the number of questions you
can ask, in which case the problem makes no sense as it becomes trivial.
In the real problem you can only ask one question, period.
(Curiously, that also means that having two guards is redundant. One
guard is enough.)
--
- Warp
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"Warp" wrote:
> The vast majority of people pose the problem like that, and they all get
> it wrong. That's because that is not limiting the number of questions you
> can ask, in which case the problem makes no sense as it becomes trivial.
>
> In the real problem you can only ask one question, period.
Yes I see that now.
> (Curiously, that also means that having two guards is redundant. One
> guard is enough.)
Sure, but having two makes the question trickier for ones who are unfamiliar
with the riddle, because it makes it seem like there are more factors
involved.
Rune
--
http://runevision.com
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Rune <aut### [at] runevisioncom> wrote:
> > (Curiously, that also means that having two guards is redundant. One
> > guard is enough.)
> Sure, but having two makes the question trickier for ones who are unfamiliar
> with the riddle, because it makes it seem like there are more factors
> involved.
I wonder if it could work with more doors than two (ie. still having
one guard and one question, or if it's impossible, perhaps two questions).
--
- Warp
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Darren New wrote:
> Eero Ahonen wrote:
>> Rune wrote:
>>> There are two passages of which you must choose one. One of them
>>> leads to freedom, the other one to doom. Once you have chosen one,
>>> you are stuck with it. In front of each passage is a guards. One
>>> guard always tell the truth and one always lies. You don't know which
>>> does what. Now you must find out which passage to choose by asking
>>> the guards questions...
>>
>> Solving which one is which is actually easy.
>
> The actual puzzle is that you only get to ask one question.
>
> I've also seen it done with three creatures, one who tells the truth,
> one who lies, and one who picks at random. Except they don't speak your
> language: they speak a language where Jay and Dook mean yes and no, or
> maybe no and yes.
>
> The solution is along the lines of "Would the second person answer Dook
> to the question of what the third person would answer if and only if the
> work Jay means "yes" in my language?" Really convoluted, but it works out.
>
And in the puzzle stated in the top post, you'd have a change of 1/3 of
being stabbed.
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> The solution is along the lines of "Would the second person answer Dook
> to the question of what the third person would answer if and only if the
> work Jay means "yes" in my language?" Really convoluted, but it works out.
>
My head asplode.
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On Wed, 16 Jan 2008 03:11:40 -0500, Warp wrote:
> (Curiously, that also means that having two guards is redundant. One
> guard is enough.)
Not the way I've heard the question asked, which is:
"Which door would the other guard say is the safe door?"
Either way, the door indicated is not the safe door.
I guess with a single guard, you could ask the question:
"If you were to lie to me, which door would be the safe door?"
So I guess it would work after all. <g>
Jim
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Jim Henderson <nos### [at] nospamcom> wrote:
> On Wed, 16 Jan 2008 03:11:40 -0500, Warp wrote:
> > (Curiously, that also means that having two guards is redundant. One
> > guard is enough.)
> Not the way I've heard the question asked, which is:
> "Which door would the other guard say is the safe door?"
With one guard you simply have to introduce the question with something
like "assume that there's another guard here and that he always tells
the truth if you always lie and vice-versa".
--
- Warp
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And lo on Wed, 16 Jan 2008 06:33:19 -0000, Darren New <dne### [at] sanrrcom>
did spake, saying:
> Invisible wrote:
>> http://www.xkcd.com/246/
>
> I saw a great solution where the wizard started explaining to everyone
> how the logic works and the warrior just shot one of them in the foot.
>
> Left: "Ow! You shot me in the foot!"
> Right: "No he didn't!"
> Left: "I can't believe you just did that!"
> Right: "Yes you can!"
http://www.giantitp.com/comics/oots0327.html
I've a soft spot for that solution too.
--
Phil Cook
--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com
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On Wed, 30 Jan 2008 05:59:34 -0500, Warp wrote:
> With one guard you simply have to introduce the question with
> something
> like "assume that there's another guard here and that he always tells
> the truth if you always lie and vice-versa".
I suppose that would work as well, though my way of asking was much
shorter.
Jim
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Jim Henderson <nos### [at] nospamcom> wrote:
> I suppose that would work as well, though my way of asking was much
> shorter.
I don't think it works.
Let's assume that door A is the save one and door B isn't.
If you ask the question to the sincere guard he would answer "if I were
to lie to you, I would say that B is the safe door".
That's the truth. Thus the lying guard would have to lie and claim the
opposite: "If I were to lie to you, I would say that A is the safe door."
Thus you can't know which door is the safe one.
--
- Warp
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