Because, well, I mean, a “biologist” would instantly react to this by assuming that both would still be poisoned. The idea that a poison (e.g. from well #6) can be a cure for another one is actually very valid (hell, even arsenic, which is very, VERY toxic, is used as a drug in certain cases of leukemia), but for a substance to be effective both as a cure and a poison (which is the cas for the substances of wells #2 to #6), it has to be quite concentrated.

Therefore, if one was to drink from well #6 to cure oneself from another poisoning, one would still be poisoned because of the still-too-high concentration of the poison of well #6 in one’s blood (my my this is a complicated sentence).

I don’t know if I was clear enough, and of course this kind of considerations should not be taken into account for what is essentially a riddle. Yet, I think this shows that different people with different background would respond in very distinct ways to this kind of question.

By the way, your blog is really, really good. I’ve learned a lot of things, and you’ve even made me want to learn C.

Bruno

PS : Sorry if there are grammar mistakes, I try to improve my English as much as I can, but the mistakes you don’t see are the worst to get ride of.

PS 2 : Would you have any advice on a good textbook on pattern recognition and signal analysis ? You mentioned it a couple of times.

1. There are no other sources of water in the Kingdom other than the wells.
2. Neither is permitted to go & drink subsequent to the duel.
3. The duel is actually: They each bring *two* glasses of well water to the duel. Each gives one glass to the othe
r to drink. Each then drinks from a glass he brought with him.
4. The Knight lives & the dragon dies. How?

The canonical answer is that the dragon brings two #6 glasses, under the assumption that he will give the Knight wa
ter for which there is no antidote, & under the assumption that whatever the Knight brings, he has the antidote for
.

The Knight drinks from well #1 prior to the duel. He drinks the #6 the dragon gives him, which is the antidote for
the #1 he had prior to the duel. He then need to drink what he brought. What did he bring? He brought a mixture
of well #1, mixed with well #2 which neutralized #1, creating a placebo.

The Knight gives the dragon a similar #1/#2 concoction. The dragon drinks the innocuous water, then poisons himsel
f with his own #6 & dies.

There you go.

I’m a programmer, by the way.
20+ years on Wall St.

1. There are no other sources of water in the Kingdom other than the wells.
2. Neither is permitted to go & drink subsequent to the duel.
3. The duel is actually: They each bring *two* glasses of well water to the duel. Each gives one glass to the other to drink. Each then drinks from a glass he brought with him.
4. The Knight lives & the dragon dies. How?

The canonical answer is that the dragon brings two #6 glasses, under the assumption that he will give the Knight water for which there is no antidote, & under the assumption that whatever the Knight brings, he has the antidote for.

The Knight drinks from well #1 prior to the duel. He drinks the #6 the dragon gives him, which is the antidote for the #1 he had prior to the duel. He then need to drink what he brought. What did he bring? He brought a mixture of well #1, mixed with well #2 which neutralized #1, creating a placebo.

The Knight gives the dragon a similar #1/#2 concoction. The dragon drinks the innocuous water, then poisons himself with his own #6 & dies.

There you go.

I’m a programmer, by the way.
20+ years on Wall St.

but now i’m 48 and don’t have time for trivialities and would ask you if you wanted to hire a person who knows all about WOW or someone who actually can do some work within the budget of your department and within the timeline of the customer.

Either you went to school and learned or else you just read WROX/o’Rielly books…talking with you for about 5 minutes would reveal that and any other “tests” like this will hint at someone having a “superiority complex” (which I mean in the nicest of ways of course).

wait another 20 years and re-read your posting…then grasshopper…you will understand

I sympathize with people who say this is a bad interview question. I even said as much in the article. I disagree on the reasons why, however.

The meat of the problem amounts to developing an algorithm (which is what an optimal strategy is). I don’t see how anyone can reject algorithm development as a necessary skill for programmers.

I think you could easily object that there’s alot of unstated rules that need to be assumed and therefore it’s a bit more of a brain-teaser or puzzler than a simple algorithm metaphor. I think that’s a valid point. But if we brush those issues aside and state the problem more clearly, it becomes a simple “make me an algorithm” question.