Can You Solve 'The Hardest Logic Puzzle In The World'?

balky12 said:
That exaclty how I interpret it.

Dragon 'X' sees two greens. Realises that they in turn can see one green therefore neither will change.
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Reading another reply above has proved a flaw in my logic though :(

2 Dragons
D1 - sees green eyes and D2 doesn't change after 1 day therefore D2 must also see green eyes, D1 then knows that he must have green eyes,
Both then change

3 Dragons
D1 - sees 2 green, thinks If I have blue, then each of the other dragons can see my blue and 1 green, so 2 Dragon scenario applies

4 Dragons
D1 - thinks that if D2 sees my blue eyes and believes his eyes to be blue also then he would assume the 2 dragon scenario to apply, however when this doesn't happen it must mean my eyes are green also.

and so on and so on


It did take some getting my head around though.
 
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^ I take my hat off to everyone who has explained it....I tried, and after about 20 minutes I gave up lol

It's not too hard to understand, but very difficult to explain
 
balky12 said:
I understand the logic.

In Dragon 1's head he can see two green eyes dragons (satisfying the new information that atleast one dragon has green eyes) and he also knows that both of these dragons can see each others green eyes (again satisfying the rule). He then accepts that neither of these dragons will change?
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You do, but you're not applying it throughout the scenario. The dragon can only accept that neither of the dragons will change for a finite amount of time because it knows that every dragon has heard the human's statement. With 3 dragons only 2 days can pass before that dragon is forced to deduce itself has green eyes.

It's easier with smaller numbers:
1 dragon being told knows it has green eyes. Poof.
2 dragons being told knows the other has green eyes, and knows that if they don't change then they must know the other has green eyes too. So it takes 2 days to make a definitive conclusion for both dragons. 3 dragons is just an extension of this.
 
Yeah the difficulty of these 'shared common knowledge' problems is being able to get ones head round the complexity of the problem when more than 3 dragons are involved.... For example when you get to 4 dragons you need to consider dragon 1's knowledge of what dragon 2 knows about what dragon 3 knows about dragon 4 etc... Its hard to explain but if a state does not exists where they must logically all have shared knowledge (and know that they all know that they do!) then the solution cannot exist.
 
So the God's one:

3 yes or no questions to either A, B or C.
A, B or C could be one of the three gods, truth, false or random.
Their answer could be ja or da? Which we don't know if it's yes or no. (forgot the proper names)

How do we work this one out then...
 
div0 said:
Agreed. It relies on them knowing that each dragon is applying the same logic process, which is not clear why they would.
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It also isn't clear why they wouldn't come to the conclusion on day 2 after none of the dragons change at the end of day 1. Is there some rule that I misread that means that they only come into contact with each other in small groups?

Wouldn't they all get to the end of day 1, realise that nobody else has changed, then all immediately conclude that because nobody else has changed that they have green eyes? That would mean that they all change at the end of day 2, not day 100.
 
glen8 said:
Grrr, struggling with the god one

No matter what question you ask, you can't determine the correct answer.
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Yeah that one is doing my head in - I think its based on trying to be clever with the old three suspects one but I can't seem to quite get this one.
 
Rroff said:
Yeah that one is doing my head in - I think its based on trying to be clever with the old three suspects one but I can't seem to quite get this one.
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mmmmm, My questions were one dimensional (ie, are you mr random) yes/no

I think the questions need to be multi-dimensional (thinking of a computer statement 'if then else')
 
Working on a route of asking a god about another god.

Ask God A 'is God B Random' - but I don't seem to get anywhere.

Too many what if's.

God A can be random/true/false and say ja or da. Still won't know anything..
 
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