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• 03-26-2009
Sebastiani
Hey that's pretty cool, though. Nice one.
• 03-26-2009
CornedBee
Riddle #3: three dwarfs, two paths, one life
Giant In the Playground Games

That's all I'll say. :)
• 03-26-2009
Perspective
Riddle #3: three dwarfs, two paths, one life
There's a whole book of these problem called Knights and Knaves, something like this:
Knights and Knaves: Knights and Knaves Logic Puzzle

Knights always tell the truth and Knaves always lie. There was a second book about Humans and Vampires. Humans always tell the truth, vampires always lie, insane humans think they are telling the truth but lie, and insane vampires think they are lying but always tell the truth. Then there's a bunch of riddles of this sort.

If you like this, also check out The Puzzling Adventures of Dr. Ecco
• 03-27-2009
abachler
Number theory in 21 minutes
Its faster to just check if a number, modulo 6469693230 has a prime remainder, since all prime numbers do.
• 03-27-2009
Tonto
Number theory in 21 minutes
The greatest common factor explanation of this is great
• 03-27-2009
Sebastiani
Number theory in 21 minutes
>> Its faster to just check if a number, modulo 6469693230 has a prime remainder, since all prime numbers do.

Are you sure about that? Can you elaborate?
• 03-27-2009
Snafuist
Riddle #3: three dwarfs, two paths, one life
Ok, just to bring this to an end:

First, you ask a random dwarf: "Who of your brothers lies more often?"

If you happen to ask A, he will correctly point to C.
If you happen to ask B, he will incorrectly point to C.
If you happen to ask C, he will randomly point to either A or B.

In either case, the dwarf not asked and not pointed to is not C.

Ask this dwarf the following question: "Which path would the dwarf suggest who is the exact opposite of you?"

If you ask A, he will tell the truth and provide you with the path that B would've suggested, i.e. the wrong path.
If you ask B, he will lie and provide you with the path that A would'nt have suggested, i.e. the wrong path.

So you take the other path.

Greets,
Philip
• 03-27-2009
laserlight
Riddle #3: three dwarfs, two paths, one life
hmm... but that seems to assume that the dwarves are benevolent. If they are (or more accurately, could be) malicious, then you have to phrase that second question more explicitly to your advantage.
• 03-27-2009
Snafuist
Riddle #5: more dwarfs
There are seven dwarfs, each one wearing a unique hat. A wind blows off the hats. The dwarfs start running after their hats and each dwarf puts on the first hat that he manages to catch. Eventually every dwarf has a hat again.

What is the probability that exactly six dwarfs are wearing their own hat now?

Greets,
Philip
• 03-27-2009
Snafuist
Riddle #3: three dwarfs, two paths, one life
Quote:

Originally Posted by laserlight
hmm... but that seems to assume that the dwarves are benevolent. If they are (or more accurately, could be) malicious, then you have to phrase that second question more explicitly to your advantage.

Right. I already had several discussions about that. The problem arises due to the inexactness of most natural languages. The most obvious solution is to ask a more concise (and more awful) question. Personally, I prefer adding the proposition to the riddle that the dwarfs are benevolent. I didn't do it in the first place because it only distracts from the intended solution, but it's good that you pointed it out.

Greets,
Philip
• 03-27-2009
laserlight
Riddle #3: three dwarfs, two paths, one life
Quote:

Originally Posted by Snafuist
The problem arises due to the inexactness of most natural languages.

I don't think so. I think that it is merely an unstated assumption. I wanted to propose the solution of just capturing the dwarves and dragging them in a direction to see their response, but then I realised that I could not be sure that the dwarves were not so bored with their existence that they intended suicide, hence I would have to ask them questions anyway :o
• 03-27-2009
Snafuist
Riddle #4: if-statement considered harmful
Oops, I skipped #4, so here it is.

Consider the following program:

Code:

```int cmp(int a, int b) {         if(a > b) {                 return 1;         } else if(a < b) {                 return -1;         } else {                 return 0;         } }```
Can you come up with an implementation that doesn't use conditionals, i.e. if, for, while, switch?

Greets,
Philip
• 03-27-2009
laserlight
Riddle #4: if-statement considered harmful
I presume that includes ternary operator, and that this is either C or C++?
• 03-27-2009
matsp
Riddle #4: if-statement considered harmful
Code:

`return (a >b)?1:(a<b)?-1:0;`
--
Mats
• 03-27-2009
tabstop
Riddle #5: more dwarfs
I would say that equals (6!/(6*5!))-1.
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