6 ms·

This kind of practice really irks me. I'm not sure what information these companies are going after, but what they're actually getting is "people who read lots

This kind of practice really irks me. I'm not sure what information these companies are going after, but what they're actually getting is "people who read lots of brain teaser books". Somehow I doubt that's what they're looking for.

Anon84 18y ago
Brain teasers are kind of extreme problem solving. Being able to tackle apparently impossible problems is a useful skill to have in most business situations. Think of it as a way to see if you can "think outside the box (tm)"
- mixmax 18y ago
  I would say that being good at brainteaser problems only proves that you're good at brainteaser problems. Nothing else.
  - raganwald 18y ago
    Yes. And no. Take yourself back to 1989 or so when very few companies asked brain teaser questions so therefore there were very few people who studied brain teasers specifically to ace job interviews. The question for an interviewer was whether being good at brain teasers correlated to being good at a programming job in a statistically significant manner. Now combine that with a number of other interview techniques, each of which correlates well and you may have had something. If you must search for reasons and meanings, it was probably because the kind of people who studied brain teasers for fun also happened to have a certain knack for the math-y problem-solving part of programming. Or they actually enjoyed solving problems for fun. Or both. I am not suggesting that we need to prove that the skill of solving a brain teaser was an important programming skill, it could be there was a root talent which expressed itself in programming and brain teaser abilities simultaneously. Or that some event in their past opened them up to learning two different and unrelated skills. All that mattered was whether you could measure a correlation. But that was then. Today, I avoid such questions entirely. However, that is because IMO it no longer correlates well. Mostly because it has become popular enough that interviewees game the system by swotting up on brain teasers, so being good at them no longer means you have innate talent for math-y problem solving, nor does it mean you enjoy solving problems for fun. So in summary I say that being good at brainteaser problems in a job interview no longer even proves that you're good at brain teaser problems, or like solving them for fun, but I disagree that it has never conveyed useful information to an interviewer.
    - mixmax 18y ago
      The post was primarily based on my (limited) experence with good hackers I know and their ability to solve brain teasers. Most of them, incidentally, are not very good at it. The sample base is small though, so it might be skewed. Also, in my opinion a lot of them are "aha" questions - once you get them they're obvious. They don't require deductive thinking, but rather that you "get" this particular question. A good example of this might be "Why are manhole covers round?" The answer is that round covers are bigger than the hole no matter how you turn them, and thus can't fall in. It's hard to deduct your way to this conclusion, yet once you get it it's obvious. Questions such as "how many pianos are there in New York?" require a bit more deductive thinking, but I'm sceptical as to how much they say about someones ability to code. But, as you point out, if there's a correlation, hoowever small, and you get other loosely correlated data it adds up.
      - harpastum 18y ago
        I agree that this type of question isn't helpful because it's so easy to memorize the 'tricks' instead of thinking about the solution, but I find it fairly simple to deduct the reason for manhole cover shapes: First, determine the requirements of a manhole cover (strong enough for semis to roll over it, movable for access, big enough for most people to fit in the hole) and the possible issues (theft, wear/tear/destruction, falling into the hole). With these requirements, it's pretty easy to design an acceptable manhole cover: 1. The manhole cover must be at least 2' in diameter to allow people to go into the hole. 2. The manhole cover should be thick metal, both to increase life and to prevent theft (some manhole covers weigh more than 80 lbs). 3. The manhole cover should have a hole/catch mechanism in it to help open it. 4. The manhole cover should not be able to fall into the hole, so should be a shape that can't fall into itself (circles are the only shape I know of that follow this). In the real world, many manhole covers do not follow all of these requirements (I've seen triangle-shaped ones), but this design outline describes the manhole covers near me pretty accurately. I would argue the 'spirit' of the question (determining whether or not the applicant can use deduction to find an answer to a tricky problem) is still extremely important--it's just that this type of problem (and especially the manhole cover example) has been gamed.
- Tamerlin 18y ago
  I don't agree. Business requirements very rarely require complex solutions, yet most "engineers" come up with stunningly complex solutions for every problem they face, no matter how simple the problem might be. Good engineers, much like good artists, simplify the solution as much as possible while still meeting its requirements.
  - Anon84 18y ago
    I said nothing about complex solutions. What I did say was "tackle apparently impossible problems", which is very different, and, as I'm sure you'll agree, extremely useful. Specially if the solution is kept as simple as possible.
    - Tamerlin 18y ago
      I agree, the point was that seemingly impossible problems rarely come up in business. Most of the seemingly impossible problems that business have are a result of overcomplex solutions to simple problems. The down side to hiring people who are good at solving complex problems, especially when they're young, is that they'll tend to solve them with complexity to make things more interesting than the simple solutions. It's good for them in the short term, bad for the company in the long term, and someone else's problem to maintain.
iigs 18y ago
Over the last few years I've spent more time interviewing than being interviewed, so I sympathize with these questions. Questions of the form "How many X are there in Y" are vanilla sizing questions, which are not first-order relevant for coding but are crucial for even the most basic engineering. The notion behind these questions is that an interviewee should be able to take a topic they're nominally familiar with (their favorite beverages, their home state), find a candidate correlation, and extrapolate (there are Y million people in my state, and the average consumer consumes X beverages per unit time, so XYtime). Questions of the form "You have X consumable Ys, how do you accomplish task Z within those X Ys", also wordable "how few consumable Xs do you need to accomplish Z" are about resource allocation or consumption, and are frequently used to ask questions about O-notation without using formulas or having programming/scripting interviewees tell you "oh I don't remember how to write bubble sort... but that's OK because every library has all kinds of sorts now" or to find out if system administrator candidates know about automation tools and how to apply them. The questions are very much not about rote memorization of brain teasers, and if the interviewer can sniff that behavior out it's _very_ negative: the interviewer most probably has no interest in the number of gas stations in Texas and will never be at the leaning tower of Pisa with two lightbulbs and an afternoon to spend. The idea is to ask one question that can test: 1) a candidate's willingness to pick up a new or unusual challenge 2) their ability to adapt what they're familiar with to solve a problem that they don't know off hand 3) the thought process involved in arriving at the conclusion Studying a list of "brain teasers" and their answers is like attempting to study a test's answer key -- it may get you through the door but it's very dishonest and a disservice to yourself as you cheat yourself out of an opportunity to expand your mind in a very relevant way using facts that aren't directly related.
russell 18y ago
I once applied for a job and got back an email asking, "You are given 9 coins, one of which is heavier. Using a balance scale, how many weighings does it take to find the heavy coin?" I wrote back, "What is the maximum number of coins that you can process in 5 weighings to find the heavy one? If you know the answer to that, then you know that I Know the answer to your question." I didn't hear back. I guess they didn't understand the algorithm or they thought I was a wise-ass. Of course I could have been filtered through HR.
- Retric 18y ago
  The answer they where looking for was "2". They where not trying to insult you just quickly discover if you where stupid like most other people sending in a resume.
  - moe 18y ago
    In reality they would only quickly discover whether the applicant could be arsed to use google...

Anon84 18y ago

Brain teasers are kind of extreme problem solving. Being able to tackle apparently impossible problems is a useful skill to have in most business situations. Think of it as a way to see if you can "think outside the box (tm)"

mixmax 18y ago
I would say that being good at brainteaser problems only proves that you're good at brainteaser problems. Nothing else.
- raganwald 18y ago
  Yes. And no. Take yourself back to 1989 or so when very few companies asked brain teaser questions so therefore there were very few people who studied brain teasers specifically to ace job interviews. The question for an interviewer was whether being good at brain teasers correlated to being good at a programming job in a statistically significant manner. Now combine that with a number of other interview techniques, each of which correlates well and you may have had something. If you must search for reasons and meanings, it was probably because the kind of people who studied brain teasers for fun also happened to have a certain knack for the math-y problem-solving part of programming. Or they actually enjoyed solving problems for fun. Or both. I am not suggesting that we need to prove that the skill of solving a brain teaser was an important programming skill, it could be there was a root talent which expressed itself in programming and brain teaser abilities simultaneously. Or that some event in their past opened them up to learning two different and unrelated skills. All that mattered was whether you could measure a correlation. But that was then. Today, I avoid such questions entirely. However, that is because IMO it no longer correlates well. Mostly because it has become popular enough that interviewees game the system by swotting up on brain teasers, so being good at them no longer means you have innate talent for math-y problem solving, nor does it mean you enjoy solving problems for fun. So in summary I say that being good at brainteaser problems in a job interview no longer even proves that you're good at brain teaser problems, or like solving them for fun, but I disagree that it has never conveyed useful information to an interviewer.
  - mixmax 18y ago
    The post was primarily based on my (limited) experence with good hackers I know and their ability to solve brain teasers. Most of them, incidentally, are not very good at it. The sample base is small though, so it might be skewed. Also, in my opinion a lot of them are "aha" questions - once you get them they're obvious. They don't require deductive thinking, but rather that you "get" this particular question. A good example of this might be "Why are manhole covers round?" The answer is that round covers are bigger than the hole no matter how you turn them, and thus can't fall in. It's hard to deduct your way to this conclusion, yet once you get it it's obvious. Questions such as "how many pianos are there in New York?" require a bit more deductive thinking, but I'm sceptical as to how much they say about someones ability to code. But, as you point out, if there's a correlation, hoowever small, and you get other loosely correlated data it adds up.
    - harpastum 18y ago
      I agree that this type of question isn't helpful because it's so easy to memorize the 'tricks' instead of thinking about the solution, but I find it fairly simple to deduct the reason for manhole cover shapes: First, determine the requirements of a manhole cover (strong enough for semis to roll over it, movable for access, big enough for most people to fit in the hole) and the possible issues (theft, wear/tear/destruction, falling into the hole). With these requirements, it's pretty easy to design an acceptable manhole cover: 1. The manhole cover must be at least 2' in diameter to allow people to go into the hole. 2. The manhole cover should be thick metal, both to increase life and to prevent theft (some manhole covers weigh more than 80 lbs). 3. The manhole cover should have a hole/catch mechanism in it to help open it. 4. The manhole cover should not be able to fall into the hole, so should be a shape that can't fall into itself (circles are the only shape I know of that follow this). In the real world, many manhole covers do not follow all of these requirements (I've seen triangle-shaped ones), but this design outline describes the manhole covers near me pretty accurately. I would argue the 'spirit' of the question (determining whether or not the applicant can use deduction to find an answer to a tricky problem) is still extremely important--it's just that this type of problem (and especially the manhole cover example) has been gamed.
Tamerlin 18y ago
I don't agree. Business requirements very rarely require complex solutions, yet most "engineers" come up with stunningly complex solutions for every problem they face, no matter how simple the problem might be. Good engineers, much like good artists, simplify the solution as much as possible while still meeting its requirements.
- Anon84 18y ago
  I said nothing about complex solutions. What I did say was "tackle apparently impossible problems", which is very different, and, as I'm sure you'll agree, extremely useful. Specially if the solution is kept as simple as possible.
  - Tamerlin 18y ago
    I agree, the point was that seemingly impossible problems rarely come up in business. Most of the seemingly impossible problems that business have are a result of overcomplex solutions to simple problems. The down side to hiring people who are good at solving complex problems, especially when they're young, is that they'll tend to solve them with complexity to make things more interesting than the simple solutions. It's good for them in the short term, bad for the company in the long term, and someone else's problem to maintain.

iigs 18y ago

Over the last few years I've spent more time interviewing than being interviewed, so I sympathize with these questions. Questions of the form "How many X are there in Y" are vanilla sizing questions, which are not first-order relevant for coding but are crucial for even the most basic engineering. The notion behind these questions is that an interviewee should be able to take a topic they're nominally familiar with (their favorite beverages, their home state), find a candidate correlation, and extrapolate (there are Y million people in my state, and the average consumer consumes X beverages per unit time, so XYtime). Questions of the form "You have X consumable Ys, how do you accomplish task Z within those X Ys", also wordable "how few consumable Xs do you need to accomplish Z" are about resource allocation or consumption, and are frequently used to ask questions about O-notation without using formulas or having programming/scripting interviewees tell you "oh I don't remember how to write bubble sort... but that's OK because every library has all kinds of sorts now" or to find out if system administrator candidates know about automation tools and how to apply them. The questions are very much not about rote memorization of brain teasers, and if the interviewer can sniff that behavior out it's _very_ negative: the interviewer most probably has no interest in the number of gas stations in Texas and will never be at the leaning tower of Pisa with two lightbulbs and an afternoon to spend. The idea is to ask one question that can test: 1) a candidate's willingness to pick up a new or unusual challenge 2) their ability to adapt what they're familiar with to solve a problem that they don't know off hand 3) the thought process involved in arriving at the conclusion Studying a list of "brain teasers" and their answers is like attempting to study a test's answer key -- it may get you through the door but it's very dishonest and a disservice to yourself as you cheat yourself out of an opportunity to expand your mind in a very relevant way using facts that aren't directly related.

russell 18y ago

I once applied for a job and got back an email asking, "You are given 9 coins, one of which is heavier. Using a balance scale, how many weighings does it take to find the heavy coin?" I wrote back, "What is the maximum number of coins that you can process in 5 weighings to find the heavy one? If you know the answer to that, then you know that I Know the answer to your question." I didn't hear back. I guess they didn't understand the algorithm or they thought I was a wise-ass. Of course I could have been filtered through HR.

Retric 18y ago
The answer they where looking for was "2". They where not trying to insult you just quickly discover if you where stupid like most other people sending in a resume.
- moe 18y ago
  In reality they would only quickly discover whether the applicant could be arsed to use google...