• anony coward (unregistered) in reply to AnteChronos
    AnteChronos:
    anony coward:

    What does simultaneously mean?

    If it means that all players must guess the color of their own hat the moment any player guesses, the highest odds you have of winning are 1 in 8.

    Not quite. The problem here is that you're thinking of "passing" in a turn-based manner. A player may say either "red", "blue", or "pass", but all players must give one of those three answers at the same time (simultaneously). So the strategy of passing if you see two hats of differing colors, and guessing the opposite color if you see two hats of the same color, results in winning 6 times out of 8.

    In which case using the word 'pass' is highly misleading and confusing. According to your understanding of the rules, the players receive their hats, take a moment to look at each other and then respond by what they see. It would be much better phrased as Once they have had a chance to look at the other hats, the players must simultaneously guess the color of their own hats or remain silent.

    It would be equally appropriate for the interviewer to disregard me for not understanding as it would be for me to disregard this boss for being unable to communicate clearly.

  • Genius (unregistered) in reply to Rodyland

    hat question... if you're allowed to move around... anyone that sees the same color hats on the other two moves to the center, if they see different colored hats they move to the out side. anyone in the middle knows his hat is opposite of the other two, if everyone is in the middle they're all the same.

  • MercPDX (unregistered) in reply to Rodyland
    • Why are manhole covers usually round?

    Because the diameter of a circle is consistent, and a round manhole cover won't fall through the hole.

  • yoshi (unregistered)

    I was in a roomful of Accenture folks today ... everyone acted and thought the same way (and dressed - seriously does accenture have an outlet store or something?). I've observed the same about Microsoft ... everyone I know in the place that handles a technical job acts and thinks alike. And yet both of them can't seem to get anything done ... or at least get it down correctly, on time, or on budget.

    Teams need to be diverse and good managers/hr personnel should look for people that have skills that balance other's skills on the team.

    These types of interviews have a habit of excluding ranges of people that would greatly benefit the organization but because they don't fit into some arbitrary mold they don't get hired.

  • Genius (unregistered) in reply to Rodyland
    Rodyland:
    - You've got a chicken, a fox, and a bag of grain on one side of the river, and a boat that holds you and one of the chicken/fox/grain. If the fox is left alone with the chicken, he'll eat it. If the chicken is left alone with the grain, he'll eat it. How do you get all across the river so that nobody/nothing gets eaten.

    BBQ the chicken, blame it on the fox, and claim crop insurance.

    it might not get you a programming job, but if you're going for sales or marketing....

  • sinrtb (unregistered) in reply to Grandpa

    have everyone but the person that sees 2 colors pass and guess opposite of the 2 colors.

  • Steve Cammarata (unregistered)

    I interviewed at Microsoft several years ago and got asked the following brain teaser: Given a rectangular piece of sheet metal with a rectangular hole in it, where the hole is not in the center of the sheet metal, how can you make one straight-line cut that results in two pieces of sheet metal with equal surface area? My answer: "Well since it's made of metal, melt it, pour it into a level, rectangular container, let it cool off, and chop it in half down the middle." The interviewer laughed and gave me credit for a creative but incorrect answer. The correct answer was to cut a straight line that travels through the center of the hole and the center of the sheet metal. I still like my answer better...

  • rast (unregistered) in reply to Q.E.D.
    Q.E.D.:
    The HR guys as well as the project managers have way too much time in their hands. The survival instinct kicks in to save them of a horendous death of boredom and they need a bit of fun with the desperate guy looking for a job. In my $0.002 opinion, there is no value in these brain teasers, it is a complete nonsense, bullcrap. I can't see your wealth of experience nor your knowledge of the tricks of the trade

    These lameass riddles are a (weak) proxy for IQ. Ideally, the employer would sit the applicant down with a a standard IQ test, and also a test of general programming knowlege. Or maybe just the IQ test. But for various reasons (read: lawyers), they aren't willing to do this.

  • SuperJer (unregistered)

    NO COMMUNICATION means NO COMMUNICATION guys...

    Anyway, here's a simulation that proves you can win 75% of the time in the red/blue hat problem:

    http://polesocking.com/hats.php

  • atari (unregistered) in reply to TimS
    TimS:
    "o, you disqualify people simply because you are too unoriginal to come up with a ridiculous brain teaser that the candidate has already heard?"

    Wow, that's so totally not what I said. You need to read up on "strawman arguments", because you're a natural at making them.

    Here's what you said:

    TimS:
    If someone shouts out the answer immediately, and recites the answer, as memorized, from a book of problems, that's an immediate check in the "no" column for me.
    How is that different from saying you would disqualify someone simply because you are too unoriginal to come up with a ridiculous brain teaser that the candidate has [not] already heard? (I realize I forgot a word in the original statement.)
  • Ornedan (unregistered) in reply to anony coward
    anony coward:
    Grandpa:
    Three players enter a room and a red or blue hat is placed on each person's head. The color of each hat is determined by a coin toss, with the outcome of one coin toss having no effect on the others. Each person can see the other players' hats but not his own.

    No communication of any sort is allowed, except for an initial strategy session before the game begins. Once they have had a chance to look at the other hats, the players must simultaneously guess the color of their own hats or pass. The group shares a hypothetical $3 million prize if at least one player guesses correctly and no players guess incorrectly.

    What strategy would you use?

    Once they have had a chance to look at the other hats, the players must simultaneously guess the color of their own hats or pass.

    This little piece of syntax here is vague, and the whole challenge centers on it.

    What does simultaneously mean?

    If it means that all players must guess the color of their own hat the moment any player guesses, the highest odds you have of winning are 1 in 8.

    Setting aside the fact that passing may be used for 'communication' which violates the rules of the riddle, after any number of passes there will always be some important pieces of information which cannot be known.

    The odds of winning are 6/8, assuming you use the correct strategy, which - as per the rules - you decided in the strategy session before you got the hats. To find out the correct strategy, see the rest of this bloody thread. Of course, with people like you failing at comprehension, you're probably correct about the actual chances of victory.

    To anyone so hung up on the word "simultaneous", consider a logically equivalent contest, where "Three players enter a room and a red or blue hat is placed on each person's head. The color of each hat is determined by a coin toss, with the outcome of one coin toss having no effect on the others. Each person can see the other players' hats but not his own." is replaced with "Three players are separated from each other and given hats, the colour of which is determined by an unbiased source of random bits out of a choice of either blue or red. Each of the players are told the colour of the other two players' hats, but not their own. Each player then chooses one of blue / red / pass, indicating their guess of their own hat's colour."

  • AdT (unregistered) in reply to Grandpa
    Grandpa:
    Three players enter a room and a red or blue hat is placed on each person's head. The color of each hat is determined by a coin toss, with the outcome of one coin toss having no effect on the others. Each person can see the other players' hats but not his own.

    No communication of any sort is allowed, except for an initial strategy session before the game begins. Once they have had a chance to look at the other hats, the players must simultaneously guess the color of their own hats or pass. The group shares a hypothetical $3 million prize if at least one player guesses correctly and no players guess incorrectly.

    What strategy would you use?

    Exactly one person makes a random guess. That makes a 50% chance for winning the prize. Who makes the guess is decided beforehand.

    "How would you determine the weight of a Boeing 747?"

    Easy, by weighing it up with Xboxes 360 and multiplying with 8.5lbs.

    Alternatively, I'd throw it in the ocean and measure the increase of global sealevels.

    No, seriously, I would look it up in Wikipedia, err, I mean Microsoft Encarta, of course.

    "Given an opaque box with three light bulbs inside and three switches outside, how would you determine which switch corresponded to which bulb if the box could be opened only once and only after all the switches were permanently set?"

    Assuming that all switches are off at first, I would enable two switches (let's call them A and B), wait a few minutes, turn off B and open the box. Now the A bulb is on and hot, the B bulb is off and hot, and the C bulb is off and cool.

  • Q.E.D. (unregistered) in reply to rast
    rast:
    Q.E.D.:
    The HR guys as well as the project managers have way too much time in their hands. The survival instinct kicks in to save them of a horendous death of boredom and they need a bit of fun with the desperate guy looking for a job. In my $0.002 opinion, there is no value in these brain teasers, it is a complete nonsense, bullcrap. I can't see your wealth of experience nor your knowledge of the tricks of the trade

    These lameass riddles are a (weak) proxy for IQ. Ideally, the employer would sit the applicant down with a a standard IQ test, and also a test of general programming knowlege. Or maybe just the IQ test. But for various reasons (read: lawyers), they aren't willing to do this.

    Come to think of, I agree with you. These brainteasers are more like I.Q. tests. I mean, you always emphasis on what you have stumbled upon in your way up to the professional ladder. I would really love to see the other way around, something like 'I didn't know this one, but can you tell me what is the result of multiplying all figures from 0 to 25 ?' Should we fire the inteviewer because it is caught by surprise and allows himself 1 minute till he figures it out?

  • anony coward (unregistered) in reply to unknown
    unknown:
    Best interview question ever...I got this after being grilled by 5 people at a company in Hackensack, NJ (you know who you are):

    "How much would the water level rise if the average annual consumption of dog food in the US were dumped into the Dead Sea"

    What the crap is that?

    Dry dog food or wet? What is its density? What is the volume of dog food consumed in the US annually? Digested or un-digested?

  • Owen (unregistered)

    The light bulb problem is easy. Turn on two switches for a minute, then turn off one just before opening the box. The lit bulb obviously goes with the "on" switch. The warm bulb goes with the switch that was just turned off.

    To measure the weight of the jet plane, measure the tire pressure in each tire on the ground. Estimate each tire's surface area touching the ground as a rectangle. Multiply each tire's pressure by the surface area and add the weights.

    The fastest bridge crossing can be done in 17 minutes with this sequence: 1 & 2 cross, 1 goes back. 5 & 10 cross, 2 goes back. 1 & 2 cross. The total time is 17 minutes.

  • rei (unregistered)

    Blame Microsoft. It's always Microsoft's fault.

  • Extra Character (unregistered)

    The 747 weight. Google it.

    The box. Trace the wiring.

    Crossing the bridge. 1 and 2 cross together. 1 returns and crosses with 5. Either 1 or 2 returns and crosses with 10 after 5 reaches the other side. Total time = 17 minutes.

    I would not get the job, because obviously MS was not looking for a Google search.

  • Senthil (unregistered)

    If I do give such an interview for whatever value it has, I would certainly give the job to the fan blow idea, it's very clever, albeit a bit cruel.

  • Idiot (unregistered)

    The chance of one hat being one color or another is always 50%, regardless of the color of the other hats.

    The fact that two hats are red does not change the odds that the third hat is blue.

    Misunderstanding of this concept is the reason casinos are profitable.

  • Grandpa (unregistered) in reply to Idiot
    Idiot:
    The chance of one hat being one color or another is always 50%, regardless of the color of the other hats.

    The fact that two hats are red does not change the odds that the third hat is blue.

    Misunderstanding of this concept is the reason casinos are profitable.

    I'll bet you a million dollars that I can give you a strategy that will win 75% of the time.

  • ms_d00d (unregistered)

    I got no such questions when I interviewed with Microsoft. Just interesting coding questions mostly relating to algorithms. And yes, I got the job. The company is not quite as evil as people make it out to be.

    Oh, and by the way...why are manhole covers round? ;-)

  • ytb (unregistered)

    It depends on where you place the importance of the "OR"

    "the players must simultaneously guess the color of their own hats or pass"

    this could be .. (simultaneously guess colour) OR (pass)
    therefore the "PASS" does not need to happen at the same time as the colour guessing ..

    I stand by my previous strategy .. tell others to Say Pass , if they can see two different coloured hats , if you hear two passes then your hat is opposite of the others .. if you hear one pass then it is the same as the person who said pass , if you hear none , then they are all the same .

  • (cs) in reply to Idiot
    Idiot:
    The chance of one hat being one color or another is always 50%, regardless of the color of the other hats.

    The fact that two hats are red does not change the odds that the third hat is blue.

    Misunderstanding of this concept is the reason casinos are profitable.

    You really live up to your pseudonym. We don't care if any given person is correct or not. That's not the point of the excercise. We care about a system of either answering or abstaining from answering that yields the highest chance that at least one person will answer correctly, and no people will answer incorrectly. This can be achieved 75% of the time, as has been explained over and over in the comments.

  • (cs) in reply to Extra Character
    Extra Character:
    Crossing the bridge. 1 and 2 cross together. 1 returns and crosses with 5. Either 1 or 2 returns and crosses with 10 after 5 reaches the other side. Total time = 17 minutes.
    That results in 19 minutes, not 17:

    1 & 2 cross: 2 minutes 1 goes back: 1 minute 1 & 5 cross: 5 minutes 1 goes back: 1 minute 1 & 10 cross: 10 minutes Total: 19 minutes

    The correct answer is as follows: 1 & 2 cross: 2 minutes 1 goes back: 1 minute 5 & 10 cross: 10 minutes 2 goes back: 2 minutes 1 & 2 cross: 2 minutes Total: 17 minutes

  • anony coward (unregistered) in reply to Ornedan
    Ornedan:
    The odds of winning are 6/8, assuming you use the correct strategy, which - as per the rules - you decided in the strategy session before you got the hats. To find out the correct strategy, see the rest of this bloody thread. Of course, with people like you failing at comprehension, you're probably correct about the actual chances of victory.

    To anyone so hung up on the word "simultaneous", consider a logically equivalent contest, where "Three players enter a room and a red or blue hat is placed on each person's head. The color of each hat is determined by a coin toss, with the outcome of one coin toss having no effect on the others. Each person can see the other players' hats but not his own." is replaced with "Three players are separated from each other and given hats, the colour of which is determined by an unbiased source of random bits out of a choice of either blue or red. Each of the players are told the colour of the other two players' hats, but not their own. Each player then chooses one of blue / red / pass, indicating their guess of their own hat's colour."

    Actually I was more hung up on the word "pass", and whether or not each person had to guess a color. If the rules are as you explain, and only one person is required to guess, then the chance of success is indeed 3/4. According to my previous understanding of the rules (all players must guess when one guesses) and the word simultaneous, the chance of success under ANY strategy is 1 in 8.

    So if an interviewer wants to determine how an applicant reacts to vaguely worded instructions, ie, do they ask for clarification or plow on and try it by themselves with limited understanding, by all means use this test as worded.

    In my interview I was asked to write pseudocode for a relatively simple problem (something like count the number of identical occurrences in an array).

    Casinos make money because the odds are always (over the long term) in their favor, not because people do not understand odds.

  • (cs) in reply to YourMoFoFriend
    YourMoFoFriend:
    gwenhwyfaer:
    No. The propensity to evaluate performance through inappropriate criteria is a pretty good indicator of WTFery.
    Thing is, you assume that it is your performance that's being evaluated. Not so. Also, while you're well within your rights to think that the criteria used were "inappropriate", you have no way of knowing if they were or not. And you never will, since you prefer to "walk out" rather then find out....

    You know what? Let's just leave it there. I think you're an arse, you think I'm an arse. I wouldn't want to work for you, you wouldn't want to hire me. Your selection procedures are clearly working for you, so hey - run with them! You'll be saving anyone like me an awful lot of hassle if we can take flight at interview, rather than having to suffer working with you.

  • Me (unregistered)

    I work at Microsoft and I hire people at Microsoft. You're absolutely wrong on every point you assert. Even the stuff you're half right about, you're still wrong on.

    Just thought I'd point that out.

  • Old Wolf (unregistered) in reply to M.G.
    M.G.:
    There is a large number of people who don't understand the 75% win strategy for the hat problem even after its been spelled out to them...
    Not one of the 50% crowd has been able to explain which step in the other posted arguments, especially the proof by exhaustion, might be wrong. Their only argument is "your solution contradicts mine so it must be wrong". (No doubt a fair comment, but when conflicting solutions to a problem are presented, the way forward involves finding problems with one of the proposed solutions).
    M.G.:
    I just hope I don't work with any of them. It reminds me of the people who can't accept that .99999999... (repeats forever) is exactly equal to 1. They refuse to accept it even though it can be proved rigorously with simple algebra, with the infinite sum of the geometric sequence rule, and with calculus.
    This one isn't so straight-forward. If you take any of those proofs you listed, you'll find they all depend on tacit assumptions about limits which are equally as hard to explain to a non-mathematician!

    It seems to me that the statement .9999... == 1 is equivalent to asserting that there is no such thing as an "infinitesimal" real number.

    This is not particularly obvious, especially when you consider the fact that in calculus, quantities such as "dx" are supposed to be infinitesimal!

    It's quite possible to have alternative algebras in which there are infinitesimal numbers, for one example see: http://en.wikipedia.org/wiki/Hyperreal_number

    So I think it is being a little harsh on those people to abuse them for not intuitively accepting our current view of real numbers, which by the way was not formalised until the 19th century -- Newton, Euler and all the other greats were unable to provide a rigorous theory of real numbers either.

    We (you and I) have worked with real numbers for so long that they are now an intuitive abstraction to us and it's hard to see them from another point of view.

  • TooLazy (unregistered)

    As far as to why manhole covers are round - I think this is fucking stupid. Yes, yes, so that it won't fall into manhole. Cool. But how about digging a square manhole? Or, in fact, any shape that is not round?

  • (cs)
    During a screening interview, I was asked how I would design a bike fit for someone visually impaired. I responded something to the effect of, "What, like, for blind people?", and she answered yes. 
    I thought for a moment and then I responded, "Well.. a blind person riding a bike doesn't sound like a very safe idea, so I would make the bike stationary, maybe with a fan blowing in the person's face. He probably wouldn't even know the difference."

She was speechless.

    Now, granted, he will not get the job. Despite the complete absurdity of the design request, and the complete practicality of his answer

    Complete practicality of the answer? Right there is some horrendous bias and superiority complex. Typical of a programmer who would code to their own needs rather than their customers'; who doesn't bother trying to understand his customers. The two reasons that spring to mind initially on why this idea isn't 'completely practicable' are that visually impaired or blind doesn't mean no sight at all, and you can still tell even without sight when your bike is stationary from simple proprioception.

    Right now I'm testing software from a programmer who doesn't understand his clients. He's wasting time on minor shit that the customers don't care about, and the primary function the customers want is "ah, no-one really cares about that". Programmers with a superiority complex need to be shown the door.

  • AN (unregistered) in reply to Ken

    Nope... Not right.. However you look at it or however you want to think about it, the chances are 50%. No matter what colour the others are wearing, you will only have a 50% chance of winning, i.e. using your logic if the others are all wearing 'BLUE' then there is 50% chance that all of you will shout out 'RED' or 50% chance only you will shout out 'RED' and win. Without any communication you cannot get a probability of higher than 50%

    /an

    Ken:
    Rodyland:
    - You have a 3 litre jug and a 5 litre jug. How do you get exactly 4 litres into the 5 litre jug?
    Fill the 5-liter jug. Pour 3 into the 3-liter jug, leaving 2. Empty the 3-liter. Pour the remaining 2 into the 3 liter. Fill the 5 liter. Pour into the 3 liter until it is full. This will take 1 liter, as it previously held 2. You now have 4 remaining in the 5 liter jug.
    Why are manhole covers usually round?
    Constant diameter. The cover cannot fall in due to being placed incorrectly.
    You've got a chicken, a fox, and a bag of grain on one side of the river, and a boat that holds you and one of the chicken/fox/grain. If the fox is left alone with the chicken, he'll eat it. If the chicken is left alone with the grain, he'll eat it. How do you get all across the river so that nobody/nothing gets eaten.
    Take chicken (leaving fox+grain). Come back (leaving chicken). Take fox (leaving grain), come back with chicken (leaving fox). Take grain (leaving chicken). Come back (leaving fox+grain). Take chicken. Done.
    Hat problem - make the strategy be: The person who sees two other people with the same colour hat calls out the opposite colour. He's got a 3/4 chance in being right. There is a 1/4 chance that they are all the same colour, in which case they'll all call out the (wrong) opposite colour.
    Hmm... (Using "0" and "1" rather than "red" and "blue".) 000 -- Result: everyone yells "1" -- wrong 001 -- silent/silent/1 -- correct 010 -- silent/1/silent -- correct 011 -- 0/silent/silent -- correct 100 -- 1/silent/silent -- correct 101 -- silent/0/silent -- correct 110 -- silent/silent/0 -- correct 111 -- 0/0/0 -- incorrect

    Six correct, 2 incorrect. That's 75%, which is better than my 50% solution.

  • anony coward (unregistered) in reply to amandahugginkiss
    amandahugginkiss:
    During a screening interview, I was asked how I would design a bike fit for someone visually impaired. I responded something to the effect of, "What, like, for blind people?", and she answered yes. 
    I thought for a moment and then I responded, "Well.. a blind person riding a bike doesn't sound like a very safe idea, so I would make the bike stationary, maybe with a fan blowing in the person's face. He probably wouldn't even know the difference."

She was speechless.

    Now, granted, he will not get the job. Despite the complete absurdity of the design request, and the complete practicality of his answer

    Complete practicality of the answer? Right there is some horrendous bias and superiority complex. Typical of a programmer who would code to their own needs rather than their customers'; who doesn't bother trying to understand his customers. The two reasons that spring to mind initially on why this idea isn't 'completely practicable' are that visually impaired or blind doesn't mean no sight at all, and you can still tell even without sight when your bike is stationary from simple proprioception.

    Right now I'm testing software from a programmer who doesn't understand his clients. He's wasting time on minor shit that the customers don't care about, and the primary function the customers want is "ah, no-one really cares about that". Programmers with a superiority complex need to be shown the door.

    In the US, the assumption is that a bicycle will be used on or near a public street used primarily automobile drivers who have, on the whole, a very poor record in the driving safety area. There are very very few cities or even rural areas with designated bike areas. So the solution is not so far-fetched.

    However, many visually impaired persons will ride a bike to work because they cannot obtain a driver's license.

    So the interviewee had some good data, but did not apply it correctly. Probably not a good candidate.

  • Robert (unregistered)

    Question by Yahoo! interviewers: How would you go about finding every single barber in Minnesota?

    Apparently incorrect answer: Google it.

  • Dude (unregistered) in reply to AN
    AN:
    Nope... Not right.. However you look at it or however you want to think about it, the chances are 50%. No matter what colour the others are wearing, you will only have a 50% chance of winning, i.e. using your logic if the others are all wearing 'BLUE' then there is 50% chance that all of you will shout out 'RED' or 50% chance only you will shout out 'RED' and win. Without any communication you cannot get a probability of higher than 50%

    OK: There are 8 possibilities for hat distributions. Here's the strategy: everyone calls 'BLUE.' The only way to lose is if they all have red hats, and the chance of that happening is 1/8, and hence you have a 87.5% chance of winning.

  • Mathematician (unregistered) in reply to Old Wolf
    Old Wolf:
    M.G.:
    I just hope I don't work with any of them. It reminds me of the people who can't accept that .99999999... (repeats forever) is exactly equal to 1. They refuse to accept it even though it can be proved rigorously with simple algebra, with the infinite sum of the geometric sequence rule, and with calculus.
    This one isn't so straight-forward. If you take any of those proofs you listed, you'll find they all depend on tacit assumptions about limits which are equally as hard to explain to a non-mathematician!

    It seems to me that the statement .9999... == 1 is equivalent to asserting that there is no such thing as an "infinitesimal" real number.

    This is not particularly obvious, especially when you consider the fact that in calculus, quantities such as "dx" are supposed to be infinitesimal!

    It's quite possible to have alternative algebras in which there are infinitesimal numbers, for one example see: http://en.wikipedia.org/wiki/Hyperreal_number

    So I think it is being a little harsh on those people to abuse them for not intuitively accepting our current view of real numbers, which by the way was not formalised until the 19th century -- Newton, Euler and all the other greats were unable to provide a rigorous theory of real numbers either.

    We (you and I) have worked with real numbers for so long that they are now an intuitive abstraction to us and it's hard to see them from another point of view.

    No, it'a a proof from a fucking definition.

    • Mathematician
  • (cs) in reply to Dude
    Dude:
    AN:
    Nope... Not right.. However you look at it or however you want to think about it, the chances are 50%. No matter what colour the others are wearing, you will only have a 50% chance of winning, i.e. using your logic if the others are all wearing 'BLUE' then there is 50% chance that all of you will shout out 'RED' or 50% chance only you will shout out 'RED' and win. Without any communication you cannot get a probability of higher than 50%

    OK: There are 8 possibilities for hat distributions. Here's the strategy: everyone calls 'BLUE.' The only way to lose is if they all have red hats, and the chance of that happening is 1/8, and hence you have a 87.5% chance of winning.

    Somebody stop this madness, I'm begging you.. anyone... please.....

    (I actually read every page, that's why... too much time in my hands during lunch...)

  • Robert (unregistered) in reply to Mark
    Mark:
    I was asked "Using nothing but your own reasoning estimate the number of barber shops in the united states." I asked what the point of the question was. They responded with "To see how your reasoning is".

    Answering the question, no matter how brilliantly, would not have guaranteed getting the job, but in any case, asking what the point of the question was certainly didn't earn you any points. Why can you still not accept at face value the reason they gave you? The point was to see how you reason things out.

  • (cs) in reply to Saladin
    Saladin:
    Quick. Given eight quarters -- one weighing more or less than the rest -- and a balance scale, if you were faced with the task of figuring out which was the odd coin out using the fewest weighings possible, what would you do?

    Obviously, I pocket the quarters and leave this stupid interview, giving me enough change to buy a Coke and pay the highway toll on the way to my next (hopefully better) job interview.

    Assuming that all the quarters look the same, I would drop the quarters on a hard surface and listen to the sound that they make. The quarter that sounds different is the one that is made from a different metal and therefore is going to weigh differently.

    Gloves.

    This solution has a O(zero) in terms of number of uses of the scale. I doubt anyone is going to find a more efficient solution than this.

    The bigger mystery is why I am replying when there are all those posts before me. (To be honest I stopped reading the replies at page 5, so I don’t know if this solution has been suggested yet.)

  • umpa (unregistered) in reply to Ken
    Ken:
    Ooh! Ooh! I know!

    Stand in a circle ...

    How many persons does it take to form a circle? Tree?

  • nameless (unregistered) in reply to Grandpa

    I am taking a simulation class right now with the professor (Ebert) that came up with that puzzle for his Ph.D...lemme tell you, one smart mother f'er

  • Huw Evans (unregistered) in reply to Genius

    Damn! You beat me to it :) This is the very solution I've just developed. Our approaches are examples of emergent algorithms. Each player has two simple rules and the desired solution emerges from each player applying them.

    Each player can see the hat colour of the other two players.

    Rule during play:

    if(the hats of the other two players are the same) move to the centre of the room else move to the end of the room

    If we enumerate the possible combinations we can see how the algorithm works:

    0s are green hats, 1s are red hats C is centre of the room E is the end of the room

    000 CCC 001 EEC 010 ECE 011 CEE 100 CEE 101 ECE 110 EEC 111 CCC

    In the first case (CCC), those wearing the green hats end up in the centre of the room, in the 2nd case (EEC), the green hat wearers end up at the end of the room. However, where they end up doesn't matter. The important point about this algorithm is that the people wearing the hats are grouped correctly.

    Rule once everyone has moved:

    if(I am in a group of three) Say the colour of the hats worn by the other two else Say the opposite colour to that worn by the member(s) of the other group

    During the game, each player is acting autonomously, they are just performing their rule. Therefore, there is no communication.

    The challenge to the reader is:

    1. To scale this type of solution to more than three participants, still with two types of hat.
    2. To scale this type of solution to more than three participants, with 3 types of hat, 4 types of hat, and so on.
    3. To ensure a correct result, even if the players don't follow their rules in the correct order (this sounds like a byzantine distributed systems problem to me, must get back to work) :)
  • trochej (unregistered) in reply to Dan

    Actually, I wouldn't be surprised if the fox ate the grain, since foxes are omnivores. :)

  • ERM (unregistered)

    I got asked by microsoft how I would design an alarm clock for a blind person. I went on and one about putting all kinds of braille on it and didn't even think of the obvious - make it completely vocal! I was trying to be too practical....

  • umpa (unregistered) in reply to Huw Evans
    Huw Evans:
    if(the hats of the other two players are the same) move to the centre of the room else move to the end of the room

    ...

    During the game, each player is acting autonomously, they are just performing their rule. Therefore, there is no communication.

    http://en.wikipedia.org/wiki/Communication

  • unknown (unregistered) in reply to anony coward

    Very nicely done, I asked all those (except for the digestion one). The response I got to all of them was more or less "I am not sure, what do you think is a good answer?"

  • unknown (unregistered) in reply to anony coward
    anony coward:
    unknown:
    Best interview question ever...I got this after being grilled by 5 people at a company in Hackensack, NJ (you know who you are):

    "How much would the water level rise if the average annual consumption of dog food in the US were dumped into the Dead Sea"

    What the crap is that?

    Dry dog food or wet? What is its density? What is the volume of dog food consumed in the US annually? Digested or un-digested?

    Very nicely done, I asked all those (except for the digestion one). The response I got to all of them was more or less "I am not sure, what do you think is a good answer?"

  • Aboyd (unregistered) in reply to YourMoFoFriend
    YourMoFoFriend:
    gwenhwyfaer:
    Or his sense of self-preservation?
    How's that? By showing that he is so full of himself that he'd rather blow an opportunity than give a riddle at least a try?
    An interviewer asking such gimmicky questions reveals he/she is an amateur, and thus working with/for such an individual is not a good opportunity at all. Therefore there is no opportunity to blow, but there is time to save by cutting it short. Thus, the only correct answer to this riddle is that it's a trick question, and the only candidate worth hiring is the one who attempts to leave in disgust.
  • vuk (unregistered) in reply to v.

    Three players enter a room and a red or blue hat is placed on each person's head. The color of each hat is determined by a coin toss, with the outcome of one coin toss having no effect on the others. Each person can see the other players' hats but not his own.

    No communication of any sort is allowed, except for an initial strategy session before the game begins. Once they have had a chance to look at the other hats, the players must simultaneously guess the color of their own hats or pass. The group shares a hypothetical $3 million prize if at least one player guesses correctly and no players guess incorrectly.

    What strategy would you use?

    the player should settle with one of the players that each of them says the different color and split the money after the game.So you have 100% chance to win the half of the money.If the interview is for Microsoft ,than you can say that you will fuck up you fellow player after the game and took all the money.

  • Anonymous Coward (unregistered) in reply to vuk
    vuk:
    the player should settle with one of the players that each of them says the different color and split the money after the game.So you have 100% chance to win the half of the money.If the interview is for Microsoft ,than you can say that you will fuck up you fellow player after the game and took all the money.

    That doesn't even make any sense. Does anyone actually read the problem? Anyone?

    I'm beginning to think at least half of the 50%/stealth-communicate/rule-misunderstanding answers on this thread are trolls trying to antagonize the rational folk.

  • Huw Evans (unregistered) in reply to umpa

    Yeah, you are right. Moving before the players announce their guess is a form of communication. Shame!

    Even though each player isn't communicating in terms of speech, a covert channel has been opened. There is no scope for anything in between each player looking at the other hats and then announcing their guess.

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