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Ask HN: What is your favourite technical interview question?

• svag 16y ago
  http://news.ycombinator.com/item?id=1840774 http://news.ycombinator.com/item?id=1840774
• spokey 16y ago
  I "stole" this question from a friend, who may not have invented it either but cultural/language barriers aside [1] I'll often ask something like: * Larry Wall wrote "We will encourage you to develop the three great virtues of a programmer: laziness, impatience, and hubris." Pick one of these three "virtues" and tell me about a time you exhibited it. [1] - Some less-than-perfectly-fluent English speakers are unfairly thrown by this question, it has a lot of relatively obscure vocabulary, and then layers irony on top. BTW, even among native English speakers the single most common response is "what is hubris"? Also, a standard although not necessarily favorite general interview question I use (technical or not) is something like: * Suppose we brought you on board at Firm X and found that you were doing an excellent job. What kinds of things could we do to reward you? followed by: * No job lasts forever. What sorts of things do you think would make you want to leave Firm X eventually?
  • svag 16y ago
    For the hubris definition, here http://www.thefreedictionary.com/hubris http://www.thefreedictionary.com/hubris :) Very interesting questions the last two, I am wondering what are the answers that you get and how do you evaluate them.
    • spokey 16y ago
      For the record, I know what "hubris" means, it's the candidates that don't. This may say something sad about the level of liberal arts education among developers. Now that I think about it, this also may say something about the candidates ability to think on their feet and/or the degree to which their curiosity exceeds their reluctance to appear ignorant, since the way the question is structured it is fairly obvious you don't need know what hubris means to answer the question. You can just pick another "virtue". I'm pretty sure that's what I'd do in that scenario, but maybe I'm less candid than others in interviews. A couple of interesting things about that first question: * My friend who introduced me to this question said he once had a candidate pick "impatience" and then proceeded to tell the story of how and why he threw a chair through a glass window during a meeting. That guy did not get the job. There probably would have been other red flags with that candidate, but it is interesting to note how few questions would likely lead to the candidate volunteering that anecdote. Throwing a chair through a window in a business setting is very bad. Not having the sense to keep that story to yourself during a job interview is the icing on the cake. * I'm surprised how often candidates will miss or choose to ignore the "pick one" aspect of the question and proceed to give one example for each. This doesn't necessarily strike me a positive or negative (actually, maybe a little positive), but it happens probably 60% of the time. * For the some candidates this can be a good "employer branding" question in the sense that it suggests the hiring manager is at least a little bit clueful and appreciative of "hacker" culture. (And vice versa. Most answers to this question are acceptable, but language/culture issues aside I'm always a little troubled by candidates that don't understand how one could possibly consider those virtues. More to the point I don't see how a good developer could not recognize the importance of a little bit of laziness, impatience or hubris to their craft.) Regrading the latter two questions: Clearly the intent of the questions are to get a sense of what motivates the potential employee (both positively and negatively). I didn't know it when I first started using them, but it turns out these questions are most valuable after the candidate has been hired, as they provides significant insight into how to manage and motivate the employee. It's nearly essential to understand how to motivate an employee, and this turns out to be an easy way to get at that information. You could (and I have) ask this question after the candidate is hired, but in my experience people are candid about different things before and after being hired, sometimes it's useful to plan for that. I've come to realize that there isn't really a bad answer to this question. (Well, maybe if the candidate couldn't come up with any reward or cause for leaving, but that's never happened.) Answers I frequently hear for the first question include "give me more money", "give me a promotion", "give me more time off" or "give me more freedom/flexibility/autonomy". There's nothing really negative about any of these answers, in fact I think each of them are pretty respectable, but more importantly they say something about what the candidate values. At some cash-strapped places I've worked the "more money" answer was a little problematic, not for anything it says about the candidate as much as it suggests they won't be happy in the environment that we could provide them. At one firm I worked at "work/life balance" was non-existent, so "give me time off" suggested a poor culture fit. For most environments I've worked in a good answer to the first question is something like "Once I've proven my competence I'd appreciate the opportunity to take on new or broader responsibilities, or to work on more interesting, more important or higher visibility projects." A good answer to the second question is something like "If I wasn't learning anything new". (An very valuable answer to the second question is something like "if my job became X" or "if I no longer had the opportunity to do Y".) Generally I'd prefer to work with people that are motivated by doing new and interesting things well, people who are willing to take on new challenges. I guess this answer also demonstrates a bit of ambition, which is a good thing in moderation. It also may show a degree of political savvy, in the sense that "pay me more", while honest, is probably not something most potential employers want to hear (at least for many job categories; on Wall Street or for a sales job I guess that might be just the answer you're looking for, but those folks are usually compensated on a commission basis to begin with).
• rdmlx 16y ago
  A technical question, or a question in a tech job interview? Non-technical: What are you passionate about? (This can tell you a lot about someone.) Technical: How would you solve problem x? (Where x is an actual problem we have had to solve working on our application. Relevancy is important and cuts through the 99 common interview questions fluff).
• burnman 16y ago
  I understand they are trying to get an idea that i have a very basic knowledge of programming, but, this has been a pretty good gauge on the quality of a company. "Define polymorphism."
  • korch 16y ago
    Maybe it's just me, and maybe I'm wrong or over-thinking it, but this question bugs me. I think this is a trick question, because there is no single right answer unless the question is prefaced with "in [language X], define polymorphism." I've lost track of the number of times I've been interviewed and had that awful question tossed at me. Without fail, every single interviewer in my experience was looking for an answer strictly in terms of whatever language(s) they're using at the company, or whatever language the interviewer is most familiar with. If you stray outside of what they know and what they're looking for, they have no idea what you're talking about. Polymorphism in Java is slightly different than for Ruby than for C than for Haskell than for yadda, yadda. No matter what, it's always going to be somewhat arbitrary and tied to some kind of language dependent implementation or feature. If your language doesn't even have classes, the answer is different, if your language doesn't have functions, it's different, etc, etc. I suppose the closest thing to a right answer would be to define it in pure mathematical terms using Turing machine notation, so as to make it universal. However I have no idea if such an answer even exists. If anyone has seen such a thing, please do share it. A better version I would ask would be: define polymorphism using x86 AT&T assembly. or: define what polymorphism represents
• DirtyAndy 16y ago
  For windows based web development: How would you create a web page that said "Hello World"? It the answer is not start notepad (I'll accept Notepad+), type in Hello World and save it as .htm or .html and put it on a webserver then for most of the places I have done interviewing for over the years they have missed the first requirement, get it done as easily and quickly as you can. I fully appreciate that this varies massively by company, and I would want to know that the person can answer certain levels of technical questions but finding people who don't overcomplicate problems is hard, finding people who learnt recursion at university or as another commentator mentioned, can define polymorphism is actually not that hard.
  • thetylerhayes 16y ago
    Interesting. Even though I fully subscribe to the minimalist notion, I would have opened notepad and at least entered valid HTML: <!DOCTYPE html> <title>Hello page</title> <p>Hello world</p> Thanks for sharing that viewpoint. I never thought of it that way. (Perhaps freelancing has made me forget good habits.)
• zem 16y ago
  programming: "how would you take a word list and partition it into sets of anagrams?". touches on some very basic data structures and algorithms, shows that the candidate is at least familiar with arrays and hashes and knows when to use which. it's amazing how many people don't get it, even when given an hour to do it on an actual computer. design (with the aid of a whiteboard): how would you go about writing a call-graph explorer? start with the high level pieces and go into more detail as asked. algorithms: "there are data structures that make tradeoffs between various operations (give examples). can you design one that has O(1) insert and O(1) extract-minimum, with everything else running in as much time as you like?" if you're asking about my favourite question i've been asked, it was "given a set of numbers from 0 to 2^n-1, with one missing, how would you find the missing number in one pass through the set and using at most n bits of extra storage" (took me embarrassingly many tries to get it, but it was a satisfying question to solve)
• phalien 16y ago
  What browser would you take with you on an isolated island?
  • Robin_Message 16y ago
    One that doesn't auto-upgrade itself (in case they send a broken upgrade, then I'll have no browser.)
• djb_hackernews 16y ago
  Not my favorite, but interesting: You are given two eggs and a hundred story building. You need to tell me, using as few drops as possible, what the highest floor you can drop an egg from and it won't break.
  • spokey 16y ago
    Is the answer you're looking for a binary search algorithm, or do you have some lateral thinking solution in mind?
    • MountainDrew 16y ago
      Because you only have 2 eggs I don't think you can use a binary search algorithm (assuming I understood the question correctly). I think you'd have to start at floor 2, if that passed then jump to floor 4, etc. until you have an egg break (lets call this floor n). Then, you go to the floor below the one that broke the egg to see if an egg survives that drop. You'll then know, using only 2 eggs the highest floor you could drop from without breaking an egg (either n, n-1, or n-2).
      • spokey 16y ago
        Spot on. I missed the 2 part, which makes this question much more interesting. By the way, I think I do could it in one drop; drop one from floor 1. If it breaks the answer is 0, else 1 because I don't think many eggs could survive a two story drop.
      • djb_hackernews 16y ago
        close. Suppose the answer is 99? How many drops would it take to figure that out? Could you do it in less?
  • babycakes 16y ago
    While I appreciate the inductive nature of this problem, this problem is more likely to demonstrate that the candidate has done a Google search for interview questions (http://www.google.com/search?q=google+interview+questions http://www.google.com/search?q=google+interview+questions) than an understanding of algorithmic theory.
• qollin 16y ago
  If I interview Java programmers I always start with letting them write a method to reverse a String on the whiteboard. ~30% fail, for the others it's an easy warmup. I then ask how much memory this method consumes and if they could think of a better way to do it if this were C and not Java. This leads to the concept of immutability of Strings and you now can have a discussion on why the Java folks chose to make String immutable in the first place...
• MountainDrew 16y ago
  When can you start?
• frankc 16y ago
  My favorite programming question to ask is: Write a function that given an integer n returns the number 1 to n in random order I find this is a good mix of not too trivial but not overwhelming, I don't expect people to come up with the fastest possible algorithm on the spot. If they code the naive solution, that's OK if it makes sense and they can describe the performance characteristics. Then we'll talk over the algorithm and I lead them to something better and see how the conversation develops.
• demiart 16y ago
  Well... the answer to that question really depends upon what set of technologies the applicant is approaching the position with. One question, however, that seems to always tell a lot about the person being interviewed is: "You are asked to mentor a new developer, fresh out of school. What habits/best-practices, language-specific and general, have you learned through your years of working that you feel should be offered to the new hire?"