• Look at me! I'm on the internets (unregistered) in reply to Khim

[quote user="Khim"][quote user="Ken"][quote user="Undefined Reference"][quote user="KattMan"][quote user="Tom Dibble"]I mean seriously, flip a coin 5 times and get 5 tails, you next flip still has a 50% probability of either heads or tails, but the law of averages states it will probably be heads.[/quote]

Fortune cookie says you best to avoid casino in future.

Seriously, there is a reason casinos hand out cards for people to track which numbers have come up in roulette.

Independence means independence. Run a simulation if you doubt this fact.[/quote] Here are the specs for the simulation:

Simulate a coin flip a billion times. Find every sequence of five sequential tails and record the value of the next flip. Print a count of 6th-flip-heads and 6th-flip-tails.[/quote]

Sequence length from 2 to 10, guessing, on any occurring sequences of the same value, that the following value will be the opposite one:

```\$ ./testrand -r 1000000000
Running...
Result: (49.9997% ones)
2: 49.9991% correct guesses (out of 1000000000 occurrences)
3: 50.0005% correct guesses (out of 500008976 occurrences)
4: 50.0019% correct guesses (out of 250001802 occurrences)
5: 49.9981% correct guesses (out of 124996040 occurrences)
6: 49.9938% correct guesses (out of 62500353 occurrences)
7: 49.994% correct guesses (out of 31254046 occurrences)
8: 49.997% correct guesses (out of 15628900 occurrences)
9: 49.9881% correct guesses (out of 7814926 occurrences)
10: 49.983% correct guesses (out of 3908391 occurrences)
```

I have to admit that this is sobering. The "law of averages" is a compelling fallacy. [/quote]

Check your conditions there. I think your statistics are a bit too consistently low. I would expect to see a couple more 50.001% in there. Although, it could be whatever random library you are using.

• Anonymous Cow-herd (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
Anonymous Cow-herd:
YourMoFoFriend:
No way. These are the same arseholes that think everything in a company revolves around them. WRONG. Business revolves around business, sales, marketing and sometimes... well customers and their needs.
Well, I'm terribly sorry for not considering the company's business needs when I weighed that job offer. I just thought turnabout was fair play.
Perhaps you should have. Especially when considering a job offer. :)) BTW, do you think there will be an offer if the company sees you as an inconsiderate type of a guy?
Before the interview, I consider what I can do for the company. After the interview, I consider what the company can do for me.
Another Anon Coward:
And all you such people are forgetting another important thing -- the point of the game is to win (i.e. get a job offer, which you can then evaluate and turn down or accept), not to be self-righteous.
Lots of people here are using the interview to evaluate the company. If they already don't like what they see, why would they bother dealing with a formal job offer? Now, I think people are describing rather crass ways to handle this. I prefer a simple, "I don't think this is really a good match. Thank you for your time, though." Really, if I know I'm not going to accept the job, for whatever reason, why should I waste more of my time and the company's time? We both have other business to attend to.

As it is, I have the luxury of being able to decline job offers simply because I don't find them interesting. Since I have that luxury, I'm certainly going to use it.

Now, let's clear up this hat thing. The strategy is: if you see two hats of the same color, pick the third color, otherwise pass. I assert that these are the possible outcomes, and that all are equally likely: Alice wears blue, Bob wears blue, Carol wears blue: all say red (loss) Alice wears blue, Bob wears blue, Carol wears red: Alice passes, Bob passes, Carol says red (win) Alice wears blue, Bob wears red, Carol wears blue: Alice passes, Bob says red, Carol passes (win) Alice wears blue, Bob wears red, Carol wears red: Alice says blue, Bob passes, Carol passes (win) Alice wears red, Bob wears blue, Carol wears blue: Alice says red, Bob passes, Carol passes (win) Alice wears red, Bob wears blue, Carol wears red: Alice passes, Bob says blue, Carol passes (win) Alice wears red, Bob wears red, Carol wears blue: Alice passes, Bob passes, Carol says red (win) Alice wears red, Bob wears red, Carol wears red: all say blue (loss) If you believe there are other possible outcomes, or that any of these is not possible, or that these are not all equally likely, please clarify why.

• Undefined Reference (unregistered) in reply to Khim
Khim:
I have to admit that this is sobering. The "law of averages" is a compelling fallacy.

The law of averages itself is not a fallacy. Only applying it to predict the future.

Again, over time, you expect the series to average to the expected value of the distribution. This is because, in the future, you expect the average of the results to be the expected value of the distribution. The average of the prior series and the expected series is as close or closer to the expected value of the distribution than the average of the prior series itself.

• OutsideInwards (unregistered) in reply to Jack
Jack:
I'm sure you know how many of the people that talk a big game on a message board can't cowboy up in real life, right?
Yeah, normally I'd be sane and go with it. It really hasn't been a good day for me (not that that's a good excuse).
• (cs) in reply to OutsideInwards
OutsideInwards:
zip:
So you seriously walked out of an interview because they asked you that \$30/\$2/\$27 question?
Yes. Brainteasers generally only test your ability to "spot the stupid trick".

Well, that's my question then -- I don't think that problem really counts spotting a stupid trick. You have a statement known to be true "paid \$30" and then a bunch of money shuffling that apparently ends in an inconsistent state. Can you find the step that created the inconsistent state, or prove that it isn't an inconsistent state?

Doesn't seem like a trick question to me.

• kftgr (unregistered) in reply to EnderGT
EnderGT:
Anonymous :
Ok, this has many WTFs in its own, but let's extend the boat ride riddle:

In one side of the river there are:

• a father with his son
• a mother with her daughter
• a security guard with a prisoner

The boat has a capacity of two, but only the father, mother and security guard can operate it.

The father can't stand the girl if her mother is on the other side of the river The mother can't stand the boy if his father is on the other side of the river The prisoner will kill any one if the guard is on the other side of the river

How can they all get to the other side of the river?

My solution, saves one trip...

```m, d, f, s, g, p
d,    s, g, p      (f, m) -->
d,    s, g, p  <-- (f)   	  m
d,       g, p      (f, s) -->  m
d,       g, p  <-- (m)	        f, s
m, d                  (g, p) -->        f, s
m, d              <-- (f)	           s, g, p
1        f               (m, d) -->           s, g, p
2        f           <-- (m)	     d,    s, g, p
3                        (f, m) -->     d,    s, g, p
4                                 m, d, f, s, g, p
```

captcha: bling

Your last 3 steps (labeled above) are wrong. Step 2, M gets annoyed by S since F is on the other side of river. Step 3, M kills S Step 4, F gets stranded on one side while M, D, G, and P move on. :)

The correct solution is:

```1        d               (f, m) -->           s, g, p
2        d           <-- (m)	     f,    s, g, p
3                        (d, m) -->     f,    s, g, p
4                                 m, d, f, s, g, p
```
• richieb (unregistered) in reply to NotanEnglishMajor
Round is the only shape that guarantees, no matter how you orient the cover, that the cover will not fall into the manhole and onto the man in the hole. That's why I only ever use round covers on my manhole.
Actually no. There is another shape that works. But that's another interview question...
• YourMoFoFriend (unregistered) in reply to Anonymous Cow-herd
Anonymous Cow-herd:
Before the interview, I consider what I can do for the company. After the interview, I consider what the company can do for me.
Wouldn't the same go for the company? They are trying to figure out whether you CAN provide what they're looking for. If they are looking for a guy who can handle a bit of pressure why wouldn't they put you in a somewhat uncomfortable situation and see how you do rather than ask "How do you do in a high pressure situation" and just trust your prepared answer? On the other note, must be nice to be able to go "Oh, they ask brainteasers on an interview. This company sucks.", and walk away... Must nice, just not very wise :)
• OutsideInwards (unregistered) in reply to zip
zip:
Can you find the step that created the inconsistent state, or prove that it isn't an inconsistent state?

Doesn't seem like a trick question to me.

No, it is a trick question because it pretty much just amounts to making the person being asked look stupid for not knowing the answer (assuming s/he did not know already know the answer). Yes, this particular question is fairly easy to work out, but most people will find that their brain simply malfunctions when put into a position of answering a question like this when not expecting it. (Similar to people on game shows looking like freaking idiots when they can't answer the most simple of questions that even early elementary school children would know.)

• kftgr (unregistered) in reply to richieb

Manhole questions...

Ask who uses the manhole and what their concerns are:

1. Sewer worker would be concerned of not only safety (dropping inside), but also ease of access to the hole. So a question of diameter and area of the hole would matter.

2. Drivers (and by extension, the City) would want manholes that are least likely to wobble and are strong.

3. The City, who are paying for them would like ones that are cheap and also hard to steal.

• YourMoFoFriend (unregistered) in reply to OutsideInwards

[quote user="OutsideInwards"][quote user="zip"]No, it is a trick question because it pretty much just amounts to making the person being asked look stupid for not knowing the answer (assuming s/he did not know already know the answer). Yes, this particular question is fairly easy to work out, but most people will find that their brain simply malfunctions when put into a position of answering a question like this when not expecting it. (Similar to people on game shows looking like freaking idiots when they can't answer the most simple of questions that even early elementary school children would know.)[/quote]Seems to me you just proved your opponents point, since all these puzzles are not used to find out your ability to solve complex problems on a spot, but rather to test your reaction to them and see your approach to solving them... Look, if you're being interviewed for a position that requires any customer interaction at all, how can the company be confident you won't call their customers stupid and storm out the room even if the customer IS STUPID? I can tell you that walking out of an interview does not help a bit. :))

• (cs) in reply to OutsideInwards
OutsideInwards:
most people will find that their brain simply malfunctions when put into a position of answering a question like this when not expecting it.

If the position being interviewed for is even remotely client-facing, the trait of having your brain "simply malfunction" when put in an "unexpected position" is not desirable.

I don't know what kind of position you were interviewing for, but if it's your opinion that "most people" will melt down when faced with this question doesn't that make it valid? I don't want to hire "most people."

• OutsideInwards (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
On the other note, must be nice to be able to go "Oh, they ask brainteasers on an interview. This company sucks.", and walk away... Must nice, just not very wise :)
This is exactly the attitude companies want to see. Apathy and/or fear from employees (potential employees) preventing them from questioning their tactics is precisely how said companies get away with questionable tactics more and more. For example, at a previous employer, they started demanding all the salaried employees work at least 60 hour weeks (threatening to fire anyone who didn't at least hit 60 hours). Most employees seem to just do it because they're afraid of the big bad boss (and getting canned). And the reason employers have this power? Because the employees give them that power by being apathetic and/or afraid.
• OutsideInwards (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
Look, if you're being interviewed for a position that requires any customer interaction at all, how can the company be confident you won't call their customers stupid and storm out the room even if the customer IS STUPID? I can tell you that walking out of an interview does not help a bit. :))
When did we limit the interview to interviews where customer interaction is required? Regardless, brainteasers (as used to gauge ability to solve such or to assess an ability to work through a problem) are similarly inappropriate for assessing customer interaction capability.
• OutsideInwards (unregistered) in reply to zip
zip:
If the position being interviewed for is even remotely client-facing, the trait of having your brain "simply malfunction" when put in an "unexpected position" is not desirable.
There are various types of "unexpected". Until fairly recently, being asked a brainteaser in an interview would have qualified as the type in which most people (supportive data non existant, but you know it is true) would have a brain fart/malfunction if it were not a brainteaser they had previously heard (or similar to one that had been previously heard). This is a far cry different than the "unexpected" customer interaction specialists (salespeople) train for.
zip:
I don't know what kind of position you were interviewing for, but if it's your opinion that "most people" will melt down when faced with this question doesn't that make it valid? I don't want to hire "most people."
If you don't want to hire somebody because their brain gets tied in a knot around trick questions designed to get people's brains tied into knots, then so be it...
• (cs) in reply to OutsideInwards
OutsideInwards:
YourMoFoFriend:
On the other note, must be nice to be able to go "Oh, they ask brainteasers on an interview. This company sucks.", and walk away... Must nice, just not very wise :)
This is exactly the attitude companies want to see. Apathy and/or fear from employees (potential employees) preventing them from questioning their tactics is precisely how said companies get away with questionable tactics more and more. For example, at a previous employer, they started demanding all the salaried employees work at least 60 hour weeks (threatening to fire anyone who didn't at least hit 60 hours). Most employees seem to just do it because they're afraid of the big bad boss (and getting canned). And the reason employers have this power? Because the employees give them that power by being apathetic and/or afraid.

So basically you want your fellow programmers to negotiate with the exact same values that you use. Fair enough -- I think we'd all like to be part of a union that catered to exactly what we wanted.

It's just not going to happen, though.

• YourMoFoFriend (unregistered) in reply to OutsideInwards
OutsideInwards:
This is exactly the attitude companies want to see. Apathy and/or fear from employees (potential employees) preventing them from questioning their tactics is precisely how said companies get away with questionable tactics more and more. For example, at a previous employer, they started demanding all the salaried employees work at least 60 hour weeks (threatening to fire anyone who didn't at least hit 60 hours). Most employees seem to just do it because they're afraid of the big bad boss (and getting canned). And the reason employers have this power? Because the employees give them that power by being apathetic and/or afraid.
Companies do what they do because there is a good business reason for it or sometimes just because they can. If and when they do this sh|t to you as an employee, then you show your backbone. If you're that good - you got nothing to worry about :) Storming off an interview hardly qualifies. For starters you assume their interviewing practices are stupid and indicative of the company's culture. Not true on both counts. Usually there is a good reason why they ask what they ask (not always of course). And at least in my experience working for a company that did ask puzzles is no different from working for the one that didn't. OK, enough theory already, just look at this thread!!! We're up to what, 15 pages of comments now and still getting "50% probability" answers? It's been said a hundred times already "forget about solving the puzzle, that's not why they're used" and still there are load of folks going "puzzles suck, they just test whether I can solve puzzles, nothing else..." Sad. Very sad.
• OutsideInwards (unregistered) in reply to zip
zip:
So basically you want your fellow programmers to negotiate with the exact same values that you use.
Not quite what I was saying. All I'm saying is that so long as employees remain apathetic and/or afraid to stand up against tactics they [individually or collectively] feel are unjust, the employers will continue their creep of injecting questionable tactics into the trade.
zip:
Fair enough -- I think we'd all like to be part of a union that catered to exactly what we wanted.

It's just not going to happen, though.

I didn't say it would (at least not until some critical point of "collective tread" is reached).

• (cs) in reply to OutsideInwards
OutsideInwards:
ntil fairly recently, being asked a brainteaser in an interview would have qualified as the type in which most people (supportive data non existant, but you know it is true) would have a brain fart/malfunction if it were not a brainteaser they had previously heard (or similar to one that had been previously heard).
OutsideInwards:
If you don't want to hire somebody because their brain gets tied in a knot around trick questions designed to get people's brains tied into knots, then so be it...

I strongly disagree with your assertion that everyone panics/brain farts/malfunctions when faced with trick questions or unexpected questions, especially in an interview.

Frankly I think it's less common than you think, especially among talented programmers. Not a 1:1 correlation, but still, I don't think good programmers melt down on math teasers as often as you're suggesting.

• YourMoFoFriend (unregistered) in reply to OutsideInwards
OutsideInwards:
When did we limit the interview to interviews where customer interaction is required?
We didn't. We also did not limit them to interviews for positions where you sit in your corner all day doing your code, never talking to anyone, not part of a team, never do any tech support, don't have to gather requirements, do not talk to Business Analysts, e.t.c, e.t.c, e.t.c... You know, the position that don't require you to do what software engineers have to do daily :)
Regardless, brainteasers (as used to gauge ability to solve such or to assess an ability to work through a problem) are similarly inappropriate for assessing customer interaction capability.
Right, keyword here "as used to gauge ability to solve such" - that is what them puzzles are usually NOT used for. As for "to assess an ability to work through a problem" what can be better than a puzzle? A hypothetical "real world scenario"? But most of the puzzles discussed here can be rephrased as real world "hypothetical problems", it's just more fun in a puzzle form. Plus, we're not talking just about puzzles here, what about questions that do not have an answer like that "tooth fairy" one? That is definitely not used to see if you can "solve" it but rather how would you approach it... Still walking out? :)
• James McGill (unregistered) in reply to vt_mruhlin

"Course the person who answers that correctly probably just heard it before. Nobody thinks about weighing quarters that fast."

Funny you should say that, because I did think of exactly that divide-and-conquer approach.

I recently had an interview at a place where I really wanted to work, was willing to take a substantial pay cut to work there, and yet, the interview was "from hell" in some ways.

They asked me to describe how I'd move the mountain range on the North side of our town, to the South.

The dealbreaker, I think, was when I refused to talk about the Spring framework as a single entity (I consider it a bag of independent technologies), and when I insisted that AJAX was nothing but Javascript and XHR, nothing really special or magical about it. (If you know me, you realize I'm way qualified to speak on this subject.)

I don't think one of the people interviewing me liked my answers at all, and I ended up taking a totally different job, and never even called them back. Really strange too, because I was more than willing to start working for them right away, or at least I was, before that interview.

• OutsideInwards (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
If and when they do this sh|t to you as an employee, then you show your backbone. If you're that good - you got nothing to worry about :)
Agreed.
YourMoFoFriend:
Storming off an interview hardly qualifies.
I've not been talking about storming off. In my particular experience, they explained why they were asking the brainteaser, and I explained why I thought it was not appropriate and that I was not interested in such a company (because in my experience, it is indicative of certain company/managerial behaviors that are not intune with what I want in an employer).
YourMoFoFriend:
For starters you assume their interviewing practices are stupid and indicative of the company's culture.
First, the way the questions are asked and answers are answered is indicative. Second, assumptions are also being made (not just in the one direction you proscribe above). These assumptions can be subconscious, but they always influence the end decision. I just prefer to get it out of the way early that if a brainteaser is going to be the main judgement point on whether or not I'll be hired (as in the case I specifically experienced as touched on in an earlier post), I'd rather not participate. As someone else pointed out, I'm not totally against brainteasers as such in the interview, but it had darn tootin' better be somewhat relevant and not something along the lines of "oh, if you don't get the right answer to this, yer a n00b we won't even consider".
YourMoFoFriend:
Not true on both counts. Usually there is a good reason why they ask what they ask (not always of course).
I'd say usually there's not a good reason. It may have started with having a good reason ....
YourMoFoFriend:
And at least in my experience working for a company that did ask puzzles is no different from working for the one that didn't.
Great for you, but I'd say you're in the lucky few crowd then.
YourMoFoFriend:
OK, enough theory already, just look at this thread!!! We're up to what, 15 pages of comments now and still getting "50% probability" answers?
Okay, maybe I'll grant that one question is probably a good for weeding out weak candidates. ;)
YourMoFoFriend:
It's been said a hundred times already "forget about solving the puzzle, that's not why they're used" and still there are load of folks going "puzzles suck, they just test whether I can solve puzzles, nothing else..."
Perhaps because a lot of people are experiencing them being used in this way? (Like in the 4 interviews I had before I landed my current job.)
• OutsideInwards (unregistered) in reply to zip
zip:
OutsideInwards:
If you don't want to hire somebody because their brain gets tied in a knot around trick questions designed to get people's brains tied into knots, then so be it...

I strongly disagree with your assertion that everyone panics/brain farts/malfunctions when faced with trick questions or unexpected questions, especially in an interview.

I didn't say everyone.

zip:
Frankly I think it's less common than you think, especially among talented programmers. Not a 1:1 correlation, but still, I don't think good programmers melt down on math teasers as often as you're suggesting.
I think it's less common now because more and more it's almost expected to occur in the interview.
• James McGill (unregistered) in reply to XenonXavior

"This means on several thousand spins of the wheel, you may see a few extra occurances of one number, and fewer of another. To take advantage of this you shouldn't bet on the unseen values, but rather on the values that occur most often."

To really take advantage of this, you should be the house and choose those locations for the 0 and 00.

• OutsideInwards (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
We didn't. We also did not limit them to interviews for positions where you sit in your corner all day doing your code, never talking to anyone, not part of a team, never do any tech support, don't have to gather requirements, do not talk to Business Analysts, e.t.c, e.t.c, e.t.c... You know, the position that don't require you to do what software engineers have to do daily :)
The difference though is that [many of the] latter points you mention are generally understood to correlate with the job. Customer interaction isn't. [I get my specs from the administrative assistant of the customer relations manager, who [administrative assistant] gets it directly from the customer.]
YourMoFoFriend:
Regardless, brainteasers (as used to gauge ability to solve such or to assess an ability to work through a problem) are similarly inappropriate for assessing customer interaction capability.
Right, keyword here "as used to gauge ability to solve such" - that is what them puzzles are usually NOT used for.
That may be true for you (and great for you if so), but in my experience, and apparently the experiences of others, says this is what they are commonly used for.
YourMoFoFriend:
what about questions that do not have an answer like that "tooth fairy" one? That is definitely not used to see if you can "solve" it but rather how would you approach it... Still walking out? :)
I will grant that I wouldn't walk out just because a brainteaser was asked. The way in which the brainteasers are asked in conjunction with the perceived intention of the brainteaser is what would cause me to choose to "walk out" or not. If the tooth fairy question were "how would you go about estimating the number of stops the tooth fairy makes per night", I'd approach in a manner you'd probably expect. If it were rather "How many stops does the tooth fairy make per night" and a decision on whether or not to hire me were based on whether I was +/- N from the "correct" answer, yer darn-tootin' I'd walk out.
• YourMoFoFriend (unregistered) in reply to OutsideInwards
It's been said a hundred times already "forget about solving the puzzle, that's not why they're used" and still there are load of folks going "puzzles suck, they just test whether I can solve puzzles, nothing else..."
Perhaps because a lot of people are experiencing them being used in this way? (Like in the 4 interviews I had before I landed my current job.)
Well, if your only tool is a hammer all problems start to look like nails :)). There will always be idiots using an otherwise valuable technique inappropriately. Such is life. Problems start when you as an interviewee assume that just because they use the technique they must be idiots... :) Here is my real interview story: I was asked "What is the difference between Oracle and MSSQL?". At first I thought the question was stupid, but then I thought "well, maybe there is something behind it, maybe they want to see my approach to this", so I asked a bunch of clarifying questions such as "From whose perspective, developer, dba, end user?", "Differences in TSQL, supported platforms or something else?"... Turns out that the person WAS indeed stupid and in her limited knowledge of RDBMS this question as asked not only made sense, but also had an answer which she was expecting (she was looking for me to point out syntactical differences in SQL implementations). Now THAT I consider a stupid question, and given that the person asked was supposed to be my future boss, I did not bother going for the second round of interviews. Was I right? Dunno. But at least I gave the stupid thing a shot. I'd much rather be asked a teaser than this nonsense :).
• Old Wolf (unregistered) in reply to KattMan
KattMan:
Man ok, I have to concede on this one, a million test cases fully random, with verifiable code. If I waited for the series and bet I still win about half the time, not more than half.
Might be less confusing if we write it up formally.

Your hypothesis was: "The result of a roulette spin depends on previous ones".

You executed a computer program which measures how much a spin depends on the previous ones, and found that amount to be "very close to none".

Your conclusion is that the hypothesis is false (and also that the measurement "very close to none" actually represents a true value of "none" with a small margin of error in the experiment).

Some people may ridicule that it took you a computer program to convince you of what is "obvious" (i.e. a roulette ball has no 'memory' as such). Ignore that criticism -- there's never anything wrong with testing out 'obvious' assumptions via an experiment; in fact doing exactly that has led to some important unexpected discoveries in the past!

• James McGill (unregistered) in reply to akatherder

Does the interviewer care about me?

Depends. The way I understood it, he was only looking for single barbers.

• YourMoFoFriend (unregistered) in reply to OutsideInwards
OutsideInwards:
The difference though is that [many of the] latter points you mention are generally understood to correlate with the job. Customer interaction isn't. [I get my specs from the administrative assistant of the customer relations manager, who [administrative assistant] gets it directly from the customer.]
That is rare. Nice but rare. So far EVERY job I ever had had some level of customer interaction, be they outside customers or internal customers.
YourMoFoFriend:
I will grant that I wouldn't walk out just because a brainteaser was asked. The way in which the brainteasers are asked in conjunction with the perceived intention of the brainteaser is what would cause me to choose to "walk out" or not. If the tooth fairy question were "how would you go about estimating the number of stops the tooth fairy makes per night", I'd approach in a manner you'd probably expect. If it were rather "How many stops does the tooth fairy make per night" and a decision on whether or not to hire me were based on whether I was +/- N from the "correct" answer, yer darn-tootin' I'd walk out.
Come on, who is going to ask you "how would you approach..."??? The whole point is to see HOW you'd approach the problem as presented :), that's perhaps the most important part... and really, if they judge you by +/-N from a "correct" answer, they do not deserve to be in business :)) Though in my experience on both sides of the table I've never heard of someone being that stupid to actually expect on an interview a real answer to the tooth fairy question, or to expect a correct answer to any puzzle for that matter. I guess I was lucky :))
• Aboyd (unregistered) in reply to Another Anon Coward
Another Anon Coward:
All you people getting mad at the interviewer are forgetting one thing -- your competition, the OTHER applicants, among whom will undoubtedly be someone who impresses the interviewer with his or her approach to the game.
The person has walked out. They don't CARE about other applicants. They aren't trying to compete. They chalk the job up as crap, and go find a different one.

Say there is a guy who stands in front of two video game displays -- one of Mario Kart and one of Halo -- and he mutters "hate shooters" and starts playing Mario Kart. Is it sensible for the Halo players to shout "we beat you, you totally let us OWN YOU" at him? I mean, they CAN. But does it make sense to claim you beat someone who won't even engage in the game? I ask because it seems to be the same attitude that I see here. Some people are saying "won't play that game" and others are then shouting, "but then they totally BEAT YOU!!!"

No, they don't. The player has engaged in a game with a different group. He only cares about winning or losing in the game that he/she is actively participating in.

Another Anon Coward:
And all you such people are forgetting another important thing -- the point of the game is to win (i.e. get a job offer, which you can then evaluate and turn down or accept), not to be self-righteous.
I think you are forgetting that we are no longer in the dot-com bust. I went out to interviews a month ago and in a week I had two competing offers. If I turn down one have I "lost?" It is no longer an employer's market. I wouldn't say it's an employee's market either, but it doesn't need to be. Once there are enough options, employees can choose rather than beg. And thus, this kind of "you should be grateful for the job" thinking will get repeatedly blindsided by people who say "going for a better offer, bye."

It isn't a zero-sum game. It isn't all or nothing. Getting a job offer isn't difficult in the current climate, and turning it down isn't doom. Therefore, the employees on this forum who are weighing these jobs and rejecting unappealing ones do not strike me as idiots. They are simply doing the same thing the hiring manager is doing -- evaluating a fit. And their assessments are just as legitimate.

• OutsideInwards (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
Problems start when you as an interviewee assume that just because they use the technique they must be idiots... :)
No, the problem started when they assumed I was a nail to be hit in the head with their hammer. :P When I first encountered brainteasers in interviews, I thought it was interesting (although they weren't using it right even from the beginning) and could be put to great use. It didn't take long to realize that the issue isn't "here's a new hammer, now make everything a nail", it's more of a "wow! look at this 10-ton hammer! we can pound everything even if it isn't a nail!"
• OutsideInwards (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
That is rare. Nice but rare. So far EVERY job I ever had had some level of customer interaction, be they outside customers or internal customers.
Interesting, I've not had to deal with customer interaction at all until this job (but that aspect of the job was specifically listed).
YourMoFoFriend:
The whole point is to see HOW you'd approach the problem as presented :), that's perhaps the most important part...
Agreed, that may be the point of doing it, but as I've so often seen, the point is missed by the interviewers using the tactic.
YourMoFoFriend:
and really, if they judge you by +/-N from a "correct" answer, they do not deserve to be in business :))
Again, agreed. Which is why I walk out of such. I'm afraid to find out how they are remaining in business.
YourMoFoFriend:
Though in my experience on both sides of the table I've never heard of someone being that stupid to actually expect on an interview a real answer to the tooth fairy question, or to expect a correct answer to any puzzle for that matter. I guess I was lucky :))
You're either really lucky, or I'm the one in a billion unlucky guy who nearly always gets this sort of thing.
• kurt (unregistered)

Okay, one person on the bridge must have the flashlight whenever two people are crossing. It can be done in 10 minutes.

Give the flashlight to Mr 10-Minute, and have him start across. Now each of the other three can walk across in turn while Mr 10-Minute is crossing.

It doesn't say they have to walk at the same rate. :)

• anony coward (unregistered) in reply to ZergMortron
ZergMortron:
ytb:
3 men and hats ... at the initial strategy session you tell everyone that if they see two hats of different colours , they are to say "PASS" within 30 seconds of entering the room.

If you hear 1 pass , then your hat is the same colour as the person who said pass , If you hear two passes , then your hat is the opposite colour of the other two who have the same ...

If you hear no "passes" then you all have the same colour .

Easy . and 100% correct ..

I like where you're going with this. But what I'd do, is arm my three guys with machetes. Within 30 seconds of walking into the room, if anyone sees a red hat, he yells "Pass!", and we all jump in the chopper. Then we fire the rockets, exploding the wall, and the guy with the blue hat grabs the 3 million. Then we fly into the sunset, pausing only to machinegun "ytb" to death. "JESUS CHRIST", we'll scream, "WHY DIDN'T YOU ACTUALLY READ THE DAMN PROBLEM/COMMENTS??"

Hmmm. Looks like this has higher than 75% chance of success. You get the job.

captcha: quake, in fear

• Matthew (unregistered) in reply to Saladin

The correct maximum number of weighings is 3. Pseudocode follows: coins labeled: A,B,C,D,E,F,G,H bools ABCgreater, ADgreater if(A+B+C < D+E+F) { ABCgreater = false }else if(A+B+C > D+E+F) { ABCgreater = true }else if(A+B+C = D+E+F){ if (G=A) coin H is counterfeit else coin G is counterfeit } if (A+D < B+E) { ADgreater = false }else if{ ADgreater = false }else{ if(G=C) coin F is counterfeit else coin C is counterfeit } if (ABCgreater = ADgreater) { if (G=A) coin E is counterfeit else coin A is counterfeit } else { if (G=B) coin D is counterfeit else coin B is counterfeit }

Yup, you need to record information to do it. Those that required 4 are throwing away information that could reduce the number of weighings by 1. Average number of weighings is 2.75

CAPTCHA: poindexter

• Bif (unregistered) in reply to Giedrius

This not only applies to teasers, some questions even from programming are ambiguous.

Amen!

I had an interviewer ask me what "immutable" meant. I hesitated for a second and asked "In what context?" and the interviewer launched into a very myopic explanation of the immutability of Java strings -- without even giving me a chance to answer the question. This was frustrating. If he had asked me to compare and contrast String with StringBuffer, and give examples of where each was appropriate and why, he would have gotten the information he was looking for and much more. Instead, I had to launch into a lengthy response to try to convince the guy that I actually DID know what he so patiently explained to me.

On another occasion, an interviewer asked me "What kind of tags would use in ASP?" I was pretty flabbergasted and said something like "Whatever tags you'd need to make the page..." He asked "Yes, buy what kind of tags would you use?" I said something like "Well, if I was generating an HTML page, I would start with <HTML>..." He looked at me like I was an idiot, and asked me what kind of tags I would use AGAIN. Finally, something clicked in my head and I said "Are you asking me if I know to use less than percent sign to separate the code from the markup?" And the interviewer smiled and moved on. He would have gleaned a whole lot more in less time by telling me to write an "Hello World" program in ASP on the greaseboard.

Another example of this kind of idiocy was an interviewer who asked me a question and decided that the only correct answer to the question was "Use a sniffer" and kept asking me the question until I gave him the "right" answer. Even though the first three answers I gave him were perfectly acceptable and two of them were simpler and provided better debugging information. Finally, I got angry at him and said "Okay, what do you want me to say? A sniffer? Is that the CORRECT answer?" and he got all excited and said "A sniffer" in a conspiratorial tone of voice and ended the interview.

The strangest thing is that of these three jobs, the last one, where I got pissed, is the job that I got an offer for, accepted, and it was the best place I ever worked.

• Aboyd (unregistered) in reply to YourMoFoFriend
YourMoFoFriend:
The whole point is to see HOW you'd approach the problem as presented :), that's perhaps the most important part... and really, if they judge you by +/-N from a "correct" answer, they do not deserve to be in business :)) Though in my experience on both sides of the table I've never heard of someone being that stupid to actually expect on an interview a real answer to the tooth fairy question, or to expect a correct answer to any puzzle for that matter. I guess I was lucky :))
I agree, you were lucky. In my experience on both sides of the table, these kinds of questions are used as a crutch. I concede that it may not be 100% and you may be the exception. However, I've had people ask me these questions (25 horses, 5 pirates, a few others) and they always get stuck on me delivering the exact perfect answer. In the case of 5 pirates, after 30 minutes of sorting it out in a phone interview (booooooorrrrrrriiinnng), I had the correct allotment of coins, but hadn't assigned them to the pirates the interviewer was expecting. He was insistent that I go back, retrace my steps, and say exactly who got the coins. Ugh, really? You already saw me sort out a difficult & unfamiliar puzzle. You're stuck on the last detail, which might take another 15 minutes of step-retracing, while I've got this hot phone pressed to my ear? Ugh.

And you know what? Later, I went online and found the puzzle, and discovered that there are TWO correct possible answers, and I simply had given him the one that HE didn't have written down on his paper! I'm sorry, but that's asshole-ish in my mind. And what did this interviewer have to show for hiring puzzle geniuses? A god-awful Web site for a "Web 2.0" company that apparently hadn't heard of the XMLHttpRequest Object and appeared to be stuck on Web 1.0 beta (gray background, tables with thick beveled borders, animated GIFs). My desire to "bring them up to speed" diminished rapidly in the interview and finally when I realized he was stuck on getting exactly the answer he had written down in front of him, I just said, "No, I'm not retracing my steps, I need to go pick up my kids. Bye."

Did I lose the job? Did someone else out-compete me? So what? I'd rather walk and find a sane place to be.

That kind of crap only reaffirms why, when I have been a hiring manager, I stop any employee who tries to ask riddles in an interview. It is almost always the employees who are very geeky and lacking in social skills, and they almost always latch onto puzzles as "how to do awesome interviews with no prep." Thankfully, the HR team at my last job had my back, and would train employees in a host of other interview skills.

• Hint Guy (unregistered) in reply to Anonymous Coward

Read the question more carefully. I can think of a strategy that yields a 75% chance of success. Not sure if you can do better, but you can definitely hit 75%.

• (cs) in reply to YourMoFoFriend
YourMoFoFriend:
I do not think you're an arse, and I don't know what made you think I am.
No, you don't, you poor little lamb, and I don't suppose you ever will...
• robot (unregistered)

I thought everyone knew the joke about the whore, the two condoms and the three danish topologists

• (cs) in reply to Undefined Reference
Undefined Reference:
Game or not, it is reasonable for the company to ask you to submit to this exam for employment, as it decreases their risk.
We live in a world where employers want interchangeable assembly-line operatives in every role, where real individualism and flair are banished in favour of unquestioning conformity, where people are governed by the kind of idiots who think that hollow corporate-mandated "morale boosters" are better than actually treating people like something other than SKUs, where anyone who isn't a "team player" is automatically relegated to the scrapheap, where having an ego - kind of necessary for pride in one's work and the willingness to defend one's beliefs - is a problem in the workplace, where some poor ready-brainwashed fuckwit on this thread actually thought that responding to me with "No hire, not a team player" did anything other than prove the very point I was making...

You know what? Their risks are low enough already.

• HmmIDontKnow (unregistered)

Well, I missed a few pages of comments, but I think all the "right" answers I saw re: the 2 condoms / 3 women problem are all wrong.

Quoting, they are given:

A + B A A + InsideOut(B)

I take umbrage to this solution, since if I were in the position, I would want to avoid the double-layer encounter as much as possible, as it reduces the sensation to an unacceptable level. So I propose:

A B B + InsideOut(A)

I consider this to be the optimal solution.

captcha: muhahaha

• (cs) in reply to Another Anon Coward
Another Anon Coward:
And all you such people are forgetting another important thing -- the point of the game is to win (i.e. get a job offer, which you can then evaluate and turn down or accept), not to be self-righteous.
If you can't even hold on to your integrity at the interview stage, what hope do you have of demonstrating it over the course of your employment?
• Burag (unregistered)

Some candidates are not even worth wasting time with an interview. Some people are not fit, and it's so obvious even before you start the interview with them. I tried highlighting the major problems that I see with candidates recently. Take a look: http://www.burag.com/?p=3

• Aboyd (unregistered) in reply to HmmIDontKnow
HmmIDontKnow:
Well, I missed a few pages of comments, but I think all the "right" answers I saw re: the 2 condoms / 3 women problem are all wrong.

Quoting, they are given:

A + B A A + InsideOut(B)

I take umbrage to this solution, since if I were in the position, I would want to avoid the double-layer encounter as much as possible, as it reduces the sensation to an unacceptable level. So I propose:

A B B + InsideOut(A)

I consider this to be the optimal solution.

Yeah, I did too. However, I was kindly rebuked. That solution exposes your STD (from the inside of A in step 1) to the woman, when you flip it inside out in step 3.

Of course, you and both know we don't have STDs, so it's natural that we wouldn't consider that worry. ;)

• YourMoFoFriend (unregistered) in reply to gwenhwyfaer
gwenhwyfaer:
YourMoFoFriend:
I do not think you're an arse, and I don't know what made you think I am.
No, you don't, you poor little lamb, and I don't suppose you ever will...
My bad. You're right, you are an arse. Sorry I underestimated you so much.
• (cs) in reply to Jack
Jack:
You are REALLY saying that if I were in a situation where I was out of a job, responsible for a mortgage and feeding 3 kids, myself, and my wife, and I was in a job interview for a company I wanted to work for, if I don't walk out when a person asks me a riddle I'm spineless? REALLY? Cause most people would consider that being a responsible adult.
Um, what is it about your wife that renders her unable to work? And what is "responsible" about living so far outside your means that you have to prostitute your integrity to cover it?

I'm not saying you don't have the right to act as you do - obviously you do. Just don't pretend it's anything other than a trade-off you're making; to claim that your choices are not choices, or that a compromised integrity is a sign of virtue, is an abrogation of the responsibility you take so seriously. Be conscious of what you hold dear, and of the compromises you make for its sake.

• (cs) in reply to YourMoFoFriend
YourMoFoFriend:
gwenhwyfaer:
YourMoFoFriend:
I do not think you're an arse, and I don't know what made you think I am.
No, you don't, you poor little lamb, and I don't suppose you ever will...
My bad. You're right, you are an arse. Sorry I underestimated you so much.
See? A satisfactory outcome for all concerned.
• YourMoFoFriend (unregistered) in reply to gwenhwyfaer
gwenhwyfaer:
Undefined Reference:
Game or not, it is reasonable for the company to ask you to submit to this exam for employment, as it decreases their risk.
We live in a world where employers want interchangeable assembly-line operatives in every role, where real individualism and flair are banished in favour of unquestioning conformity, where people are governed by the kind of idiots who think that hollow corporate-mandated "morale boosters" are better than actually treating people like something other than SKUs, where anyone who isn't a "team player" is automatically relegated to the scrapheap, where having an ego - kind of necessary for pride in one's work and the willingness to defend one's beliefs - is a problem in the workplace, where some poor ready-brainwashed fuckwit on this thread actually thought that responding to me with "No hire, not a team player" did anything other than prove the very point I was making...

You know what? Their risks are low enough already.

After calling you an arse I read this and thought "No, wait a minute, this guy is not an arse, he is a very sad man with very sad job that been interviewed too many times by stupid arses who didn't know what they were doing to the point where even one more puzzle on an interview would send him out the door screaming in horror..." Dude, this is not 1984, you can be as unconformist as you like, don't have to be an arse about it, which unfortunately you are.

• (cs) in reply to YourMoFoFriend
YourMoFoFriend:
Dude, this is not 1984, you can be as unconformist as you like
My experiences - and about 75% of responses to this thread - tell me otherwise. I can be as nonconformist as everyone else is prepared to tolerate; that isn't exactly the same, is it?

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