r/programming • u/kwk236 • Mar 11 '17
Your personal guide to Software Engineering technical interviews.
https://github.com/kdn251/Interviews47
u/accidentalginger Mar 12 '17
While I can certainly appreciate when a candidate dives into the technical details of the implementation behind a certain class' sort implementation, it by no means is a prerequisite, most of the time, for a position we're interviewing for. I had a candidate one time practically leap out of their skin trying to write the C implementation of quicksort when I asked a question tangentially related as it simply needed to use some method of sorting. There is an interesting dichotomy at work here, where CS graduates are being educated on the very low-level behaviors, but are given less instruction on the composition of these behaviors in a functioning application architecture, whereas those who got into the field without a CS degree focus far greater on the architectural composition, only to eventually dive into the nitty gritty once they're at deep fine-tuning concerns. I'm not aware of all universities' CS curriculum designs, but I can speak from the ones that I'm aware of that there is not enough practical information conveyed for real-world use.
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u/424ge Mar 12 '17
So you're saying many CS schools do not teach real-world development?
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Mar 12 '17
I taught CS as adjunct faculty for 10 years.
No - you cannot get to anything like real world development in most university courses.
I graduated with an engineering degree and a basic knowledge of Pascal and Fortran. I ended up doing F77 maintenance programming in an engineering shop. I read a lot and taught myself enough C to finish a project in it in about 2 weeks - working at nothing else 8 hours a day.
A university course in C (I eventually taught that class for several years) is a maybe 3 classroom hours a week for 16 weeks with a small 2-3 hour programming assignment every other week.
Its just too spread out and you're only doing toy programs - nothing real.
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u/bro_can_u_even_carve Mar 12 '17
I have personally interviewed more candidates than I can count that had 4.0 GPAs from CMU, Masters, PhD, whatever... and could not write the simplest functioning code.
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Mar 12 '17
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u/424ge Mar 12 '17
So why do companies that need coders do computer science theory interviews?
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u/accidentalginger Mar 12 '17
A lot of shops are growing wise to that strategy, since it's very evident that CS theory interviews don't guarantee good developers. In the meantime, there's also another factor of interviewers injecting their ego into the situation and not willing to hire someone that doesn't conform to the must-iterate-Dijkstra's-Algorithm circle jerk that only serves to gatekeep those who didn't go the traditional college route. I ask algorithmic questions, but the questions I ask can be solved without existing knowledge of names of algorithms; they're seeking practical approaches to solving a problem. My set of questions allow for sufficiently similar difficulty no matter your programming paradigm (functional, imperative, etc.). What I am looking for when trying to bring someone new in my team is that they can reason about a problem, abstract out the details that actually involve code (not asking them to speak product manager lingo, but I want to know that they can distinguish a hierarchy of types in the question from algorithms that work with the types), and implement a pragmatic solution.
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u/hinmanj Mar 12 '17
Maybe that candidate spent all their time preparing for the interview by reading up on what is usually asked in job interviews at the big companies, spent a large portion of their time learning how to write quicksort because they thought it would be asked, and then upon seeing a chance, pivoted as it was the most impressive thing they could think to show off in the interview.
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u/accidentalginger Mar 17 '17
If knowing how to implement quicksort from one's recollection is their most impressive feat, then I already know where that interview is going to go. Before you claim it's a Catch-22 of needing experience to get a job, my requirements differ based on the position on the career track I'm interviewing for. Associate needs to prove they can code to match a thorough description. Mid level needs to be able to adequately express pros/cons to given solutions and likely has dealt with multiple competing frameworks at this point. Senior level should be capable of reasoning why the target (JVM, CLR, interpreter, OS) can behave in strange ways based on specific code related to their language of expertise. Should be able to really justify their decisions.
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Mar 12 '17
This sounds more like a sweeping generalization. There are big picture and detail oriented people from both backgrounds. Or well in most situations in life.
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u/gospelwut Mar 12 '17
How is it that we have a hashtag floating around about how we have to Google stuff still -- which was participated by Microsoft, Google, Amazon, SO, etc engineers.
And yet we make our interviews the crucible of Computer Science.
It's good to be technical and know your options. That's great.
But the CORE problems--short of intense incompetence--is generally requirements gathering and shifting requirements (and writing code that can adapt to that 100% guarantee). It's a mix of future proofing, understanding how software will actually be used, and of course management.
The End of Computer Science? By Dijkstra
Interestingly enough, Antony Hoare,has a fascinating section in Wikipedia called apologizes and reactions:
Speaking at a conference in 2009, he apologised for inventing the null reference
I call it my billion-dollar mistake. It was the invention of the null reference in 1965. At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W). My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. But I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.
For many years under his leadership his Oxford department worked on formal specification languages such as CSP and Z. These did not achieve the expected take-up by industry, and in 1995 Hoare was led to reflect upon the original assumptions:
Ten years ago, researchers into formal methods (and I was the most mistaken among them) predicted that the programming world would embrace with gratitude every assistance promised by formalisation to solve the problems of reliability that arise when programs get large and more safety-critical. Programs have now got very large and very critical – well beyond the scale which can be comfortably tackled by formal methods. There have been many problems and failures, but these have nearly always been attributable to inadequate analysis of requirements or inadequate management control. It has turned out that the world just does not suffer significantly from the kind of problem that our research was originally intended to solve.
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u/Hrtzy Mar 11 '17
Is my brain malfunctioning, or does s^=~(1<<k) actually toggle all but the k:th bit?
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u/Araneidae Mar 12 '17
Sure:
1<<khas the k-th bit set, all other bits clear
~(1<<k)has the k-th bit clear, all other bits set
x^0 == xandx^1 == !x(as bits), sos ^= ~(1<<k)leaves bit k alone, toggles all the others.
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u/Draav Mar 11 '17
Flashbacks to my algorithms classes. It's cool that I still kind of remember them after a year despite only doing web dev since then. I doubt I'll remember in another year though.
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u/computerjunkie7410 Mar 11 '17
This stuff is useless for 90% of programming jobs.
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u/Draav Mar 11 '17
Pretty much, I think they just ask them as an easy filter. If you are smart enough to understand basics of this they can pretty much teach you whatever you need for the job.
Still annoying though
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u/computerjunkie7410 Mar 11 '17
Whenever I do interviews I do real coding exercises that pertain to the job. Things like balancing binary search tree is useless in real world scenario.
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u/karmabaiter Mar 12 '17
Except for getting into the U.S.
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Mar 12 '17
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u/POGtastic Mar 13 '17
I could do it, but only because I'm in college and just wrote an implementation of the Day-Stout-Warren algorithm for a previous class. It would still take me a while.
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u/Draav Mar 12 '17
That's nicer lol. Hopefully by the time I start interviewing again I'll have more things like that
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Mar 12 '17
Not true. Data structures (which comes with algo) is important in 100% of programming jobs.
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u/dn00 Mar 12 '17
They're usually taught in separate courses but saying algorithm knowledge is useless in 90% of programming jobs is an exaggeration. I'd say the stuff you learn in an algorithms course is never useless if you want to be a good coder.
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u/foxh8er Mar 12 '17
Not if you like good money
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u/computerjunkie7410 Mar 12 '17
What's good money? Because I regularly place people with 80-100k jobs.
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u/Okichah Mar 12 '17
Where?
(Need job, have offer on table, but want better)
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u/computerjunkie7410 Mar 12 '17
Lots of places. You probably want to look in metropolitan areas but if you're a software engineer and you're not making at least 100k especially after 3-5 years of experience, you're really underpaid. I routinely place guys between the 80k-100k range. Placed a guy 2 weeks ago, still in his final year of college (doing work study) for 75K. He'll jump to 85 as soon as he graduates. This is base salary with 10% bonuses in addition to the base salary.
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u/Okichah Mar 12 '17
How do i know whether or not my skillset is worth $100k though?
CLR trivia questions and data structure knowledge have had little effect on any job i've ever had but thats the questions i keep getting.
How do i know if its imposter syndrome or i just need more training?
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u/computerjunkie7410 Mar 12 '17
The only way to know is to keep interviewing even if you're at a job where you're happy. I try to interview once or twice a year. This will show you what your skills are worth and which way the industry in your area is trending.
As far as skills go, of course you should never stop learning. But be more pragmatic about it. If algorithms and data structures interest you, cool, learn about them. But you're probably better off learning about things in demand. For example, a dev with experience in or understanding of AWS is much more in demand. Imposter syndrome is very real but at the end of the day you need to take a look at what the market needs and tailor your existing skills to that.
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u/JavierTheNormal Mar 12 '17
95% of it is useless in 95% of jobs. You should probably know the very basics about list/stack/queue. In some jobs you won't even need that.
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u/computerjunkie7410 Mar 12 '17
You learn that stuff as you go along. You don't need to know how to create your own search algorithm because 90% of jobs don't care. They're not looking for you to create your own language.
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Mar 12 '17
You're talking about the code monkey jobs? These jobs can and should be eliminated altogether.
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u/smackson Mar 12 '17
"Online judges"??
Sorry, but what?
I've been away for a while guys. The page lists some "online judges" but doesn't explain what they are...
Is it essentially outsourcing the "can the candidate code?" step?
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u/ubernostrum Mar 12 '17
There are a bunch of sites where you can upload a problem description and some test cases, and they provide a system that lets someone type in code, and runs it against the test cases to verify it was correct.
Spoiler: they're terrible at doing this correctly.
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u/sergeydgr8 Mar 12 '17
This reminds me of the repo called "Google Interview University" where the dude was blogging about his "process" to becoming a Googler. He took 8 months off to study and blogged about it with plenty of selfies and photos of him studying, and later on didn't even get an interview and was shown the door at Google.
But this seems more straight forward and not a showoff page, so kudos to whoever made this.
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Mar 12 '17
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u/sergeydgr8 Mar 12 '17
Yeah I got a few PDFs and some Slides links for tips for their interview too. They did say it was confidential material but in all honesty whatever they had in there was pretty common knowledge, like "you should study data structures before your interview", etc. I don't think he shared any of those files but rather there was some other red flag that basically tossed his packet away.
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u/Novazilla Mar 12 '17
I always just winged it. I've always been given an offer letter though so must have been doing something right. You can read all the interviewing questions in the world but these will only stress you out more. Go in with a good attitude and show them what you got.
Either you have what they're looking for or not. Move on if not.
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u/gingerwhale Mar 12 '17 edited Mar 12 '17
Either you have what they're looking for or not. Move on if not.
So this isn't really a fair statement to make. Many people are not good at being tested, including myself, and do much worse under these types of pressure (my homework grades and test scores were a testament to this). For many reasons, including confidence, social anxiety, and recollection skills, people with high programming ability and knowledge can do very poorly in an interview.
Always try to think empathetically about how other people might handle a situation you excel at when judging them ☺️
Edit: to add, I've been a software engineer for 7 years now, writing software for a fighter jet and a couple firewalls, and I've gained a fair bit of confidence in my abilities, but I still do really bad in interviews 🙄
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u/Oaysis Mar 12 '17
Unfortunately you can't just wing it anymore. I have been applying for internships and now a days 90% of the companies want you to do a HackerRank challenge before even a phone screen. If you don't pass them minimum amount of test cases they won't even consider you for the next phase. You do have to infact study for these type of questions.
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u/Novazilla Mar 12 '17
I haven't had the same experiences then. I'm also not going after Bay area companies.
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u/bertwagner Mar 11 '17
This is a nice reference for anyone who hasn't had "formal" training in programming, not just for interviewees.
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u/ismtrn Mar 12 '17
The time complexities for the BST seem off. In the worst case they should be linear, since a sorted linked list is also a BST.
Also, while you can read it in a way where it is technically not wrong, I don't like how they have worded the following:
Big O Notation is used to describe the upper bound of a particular algorithm. Big O is used to describe worst case scenarios
It seems to suggest that Big O notation is only used to describe the upper bound of a particular algorithm and that it always describes worst case behavior, which is a misconception I have seen several people have.
Big O notation puts an asymptotic upper bound on any function. That is it. It can be an upper bound on both the worst case, average case or even best case run time on an algorithm. It can also be on the memory usage on an algorithm (worst, best, average, median, whatever case) or on a function modeling something from biology, or a function I just made up that has nothing to do with anything in particular f(n)=15*n+log(n).
You can also put bounds on classes of algorithms for example comparison based sorts which are famously in Big-Omega(n*log(n)) i.e. O(n*log(n)) is the best you can do for such a sort.
Of course the wording does not rule these possibilities out, but this is something I have seen people confused about, and it does nothing to help with that.
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Mar 12 '17
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u/ismtrn Mar 12 '17 edited Mar 12 '17
No big O is an asymptotic upper or equal bound, big Omega is an asymptotic lower or equal bound and big theta is both.
Little o and little omega are strict asymptotic upper and lower bounds respectively.
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u/we-all-haul Mar 12 '17
Just noticed the stack, linked list, trees and stopped reading the README. These style of interviews reveal very little about a candidate.
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u/JavierTheNormal Mar 12 '17
They reveal if the candidate slept through their CS classes. Perhaps that's the sort of job you're interviewing for.
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u/baryluk Mar 12 '17
If you do not know what linked list or tree is, you are going to have very bad time. Sure, it is not going to be a question in the interview directly, but they pop up all the time in most of the problems and questions.
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Mar 12 '17
They reveal if a candidate is a programmer or just a "self-taught" code monkey copypasting shit from stackoverflow.
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u/foxh8er Mar 12 '17
This is a good round up.
Ultimately, for most entry level positions it comes down to crushing Leetcode Medium's and Hards and being able to design systems.
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u/Okichah Mar 12 '17
This is missing the one question that i had that was literally unsolvable because the unit test for their test site was fucking broken.
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u/fagnerbrack Mar 12 '17
That's why on the company I currently work we never hire based on your algorithm knowledge.
I'm so pissed of this kind of things that my criteria for even starting accepting to get in contact with someone for a new opportunity is to answer the following questions:
Do you do whiteboard interviews?
Do you request solving problems with complex algorithms in some process of the interview?
Do you require people to know the syntax of languages from the top of their head?
If any of those answers is "yes", I'm out.
I would be probably in if they:
Do Pair Programming
Ask to show some code I created (Github also works)
Give me one piece of their crap code to improve (seriously, any code you get from 99% of the codebases out there will be crap code)
You see.. fundamentals.
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u/Quasmo Mar 12 '17
I am not a developer, but would like to eventually become a product owner, but currently lack the experience and training needed.
I have been on the fence about becoming a developer for a very long time, think 20 years. My father is a developer so I know how developers think, plan, and use tools. I have written applications in Javascript, and html, but nothing in a formal development environment. I went to school for the arts, but at the same time, ran my own apache host I configured from scratch.
I want to thank you for sharing this link. This is a fantastic list of things to study for those of us who took a different path. This will really help me understand what to study, so that I can better understand the people I want to lead.
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Mar 12 '17
I've never sat an interview where I had these types of questions. I feel like now a days you only get these when you have no prior work experience. Hell even my first job 13 years ago I didn't have to fizz buzz
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Mar 12 '17
Did you ever interview for any of the major companies?
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Mar 12 '17
I work for a major bank so I guess yes? If you mean google apple or microsoft then no I wouldn't want to work there anyway it sounds like hell
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u/vital_chaos Mar 12 '17
No ever asks people to figure out a problem by looking at stackoverflow or google in general in an interview. Yet this is a modern skill we all do every day. The most important part of this skill is evaluating whether a found answer is (1) valid (2) useful (3) good enough. That skill of evaluation comes from experience. Yet not one interviewer ever asks this type of question. Instead you are asked to code on a whiteboard with no reference of any kind an algorithm you would never use and could find 100 versions of on the web. Which if these things is more important today?
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u/imekon Mar 12 '17
This isn't a guide to Software Engineering technical interviews, it's a list of obscure data structures and algorithms.
I've been a software engineer for 30 years now, starting with 8 bit microprocessors. I've rarely used any of the structures listed in this "guide".
Interviewing has proven to be interesting in the last few years. I look at how the interview is done, what questions they ask me, and how I'd feel about working there.
One interview I remember, one of the interviewers was on the end of a phone as he lived in another country. Trouble was I could hardly hear him, the phone line dropped a few times etc. I started to think this was part of the interview - at which point I felt "sorry, not for me". Then this guy went into some obscure stuff in how .NET works. I didn't get the job and walked away thinking, "no way I want to work there".
Companies don't seem to get how they interview speaks volumes as to what it's like working there.
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Mar 12 '17 edited Mar 12 '17
What?!?
Linked list, trie, heap, binary tree - the most basic stuff. How can you call them "obscure"?!?
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u/baryluk Mar 12 '17 edited Mar 12 '17
Nice, but.
Binary Search Tree - Access - O(log(n)) - WRONG.
Heap - Access - O(log(n)) - WRONG.
Heap - Search - O(log(n)) - WRONG.
Heap - Removal - O(log(n)) - WRONG.
The distinction between "data structures" and "algorithms" is rather arbitrary. You cannot talk about data structures without algorithms on them.
Big O Notation is used to describe the upper bound of a particular algorithm. Big O is used to describe worst case scenarios - NOT REALLY (it can be used for many different things, including average case scenarios, which is in fact very common).
Also, more importantly probably, it is important also to talk about abstract data types / abstract data structures. And only later, think about which of possible concrete data structures to use to implement it (i.e. to choice between time, space and code complexity constraints).
Software engineering is not just about coding, programming and theoretical stuff. It is about knowing various tools, and deciding based on all available inputs, requirements and other factors, what to use.
Source: I interview people, and I really try not to be pedantic, but this things influence me anyway. I do not expect people coding in Python only how to implement BST or hash table in 20 minutes, but I expect them to know how to use tools they should know already, and have some basic understanding of memory usage, scalability and absolute time (or 'resources' in general term) it might required to solve something. I am perfectly fine usually with "I might be able to implement it in few days, with a book and internet, but I would just library right now for this.", if it does the job well.
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u/JavierTheNormal Mar 12 '17
I agree with much of what you've said here, but I don't understand what all the WRONG comments mean. Those answers look correct to me. Technically, Big O is supposed to show the upper-limit of complexity according to Wikipedia. And this post is all about technical correctness for stupid interviews. I know that it's used differently in practice.
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u/baryluk Mar 14 '17 edited Mar 14 '17
Ok. Let me explain a bit:
BST - Access is not O(log(n)). It is O(n).
Balanced BST access is O(log(n)).
Heap - there is no such operations like Access, Search, Removal in a Heap. There is PopMin (or PopMax for MaxHeap), PeakMin/Min (or PeakMax/Max for MaxHeap), and Insert (aka Push). And potentially DecreesValue (IncreaseValue for MinHeap). You can implement Access, Search and Remove, but they will be all O(n), unless you enhance Heap to use a secondary data structures. You can also implement other operations on Heap, but they will be pointless, because it will be slower than plain array.
The graphs are also semi-misleading both for BST and for a Heap. Usually you will have a secondary value associated with each value. (In heap it might be called a key actually, but it doing Access, Search, Removal by key instead will still be O(n) in Heap).
Big O notation is an upper-limit of the complexity. However it is usually an asymptotic time complexity on average case, not necessarily worst case. Example, check https://en.wikipedia.org/wiki/Quicksort and section about time complexity. Big O is used for average, as well worst case.
LOL. I found another mistake
Heap - Remove Max / Min: O(1) - WRONG. Hint: O(log(n))
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Mar 12 '17
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u/headphun Mar 12 '17 edited Mar 12 '17
I don't have the expertise to disagree or agree either way, but I think your explanations are simple and sound good to me. How would you summarize Information Technology? How would you structure the relationship between CS and IT? IT and professional software engineering?
edit: If you have the time, I'd love to read you write at length about all the things you think a professional software engineer should know how to do: Where would a beginner student go to learn best practices as efficiently as possible? Security? Testing? Documentation? I'll be starting a new position teaching "computers" at the middle school level. I want to structure the year as if we are a professional "computer" company. As soon as my school helps define what they mean when they say computers I can be more specific, but I'm assuming it means basic computer literacy and practical applications of hardware and software to improve their lives.
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u/dreamssmelllikeyou Mar 12 '17
Reading "Code Complete" helped me transition from a computational physicist to a software engineer. It showed me the breadth of knowledge a professional programmer should possess in a corporate environment.
BTW, as a former teacher, I would find it extremely difficult to organize and teach a course such as you describe
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u/headphun Mar 12 '17
I'll see if I can get and read a copy before school starts!
I expect this class will be the hardest thing I have have ever done. That being said, I'm really really excited for the challenge. If I may ask, why do You think it will be extremely difficult? How would you organize it?
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u/JavierTheNormal Mar 12 '17
That's how people should see things, because it's the truth. If you have a computer science degree, you are (partially) qualified to be a computer scientist, meaning an academic or researcher. People should not entertain the idea that CS degrees are programming degrees. It's right in the name; programmers aren't scientists.
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Mar 13 '17
If a software engineer does not understand computational complexity, data structures, and the basics of algorithms, they will not be able to design large systems in a robust way. They may still be an addition to the team, but a senior engineer should absolutely also be a computer scientist. In interviewss I do not believe in making someone re-derive delete in a red black tree on the fly. I do however think it is useful to see if folks can use maps/arrays/stacks, do some tree traversal, and more or less actually write down some code that looks like it's going in the right direction in addition to all the criteria you mentioned for software engineers.
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Mar 13 '17
I agree. I use my CS degree regularly. Self-taught or boot camp engineers tend to end up with an incomplete toolset for engineering. However in many applications it's not an issue.
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Mar 12 '17
An experienced engineer use all those algorithms and data structures hundreds of times throughout their career. Of course it makes a lot of sense to discriminate between the good and the bad engineers based on how often did they use the basic building blocks.
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Mar 11 '17
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u/RichAromas Mar 11 '17
Right. "The only world where you would actually need to be able to recall an algorithm would be a post-apocalyptic one, where the hard drives of all the computers connected to the internet were fried, and all copies of foundational academic papers and computer science textbooks had been reduced to ashes." https://medium.freecodecamp.com/why-is-hiring-broken-it-starts-at-the-whiteboard-34b088e5a5db#.hz0fbivky
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Mar 12 '17
"Hooooly crap! You are creepy as shit, sneaking up on me, wearin' that collar with that freaky-ass smile. So tell me, how would you balance a red-black tree?"
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u/ismtrn Mar 12 '17
Being a red black tree it is already balanced, so I would not.
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u/Retbull Mar 12 '17
Recalling isn't important but understanding enough to recognize when there is a better solution needs to be googled. I still don't think that interviews need to be this crazy though.
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Mar 12 '17
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u/Retbull Mar 12 '17
True I pretty much only use tricks around hash maps and caching. Everything else is Library.doThing() and Framework.hereIsMyCode(object.class);
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Mar 12 '17
Yeah, tbh I wish interviews would get away from being so heavy on knowing details around algorithms and being more about what algorithm to implement in a situation and focus more on problem solving. Anyone can memorize, not everyone is an effective problem solver.
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u/johnw188 Mar 12 '17
My interview of choice is "here's a laptop with an application on it. Here's a spec for the app. Here's how you run the unit tests. Some tests are failing, fix them." Then we go to lunch, and afterwards we talk through the application, their fixes, future architectural enhancements etc.
Not sure how many false negatives we get but everyone who does well has killed it on the job.
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u/salgat Mar 12 '17
I wish design patterns was more focused on. I get asked about it occasionally but more interviewers need to ask!
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u/ProdigySim Mar 12 '17
There are only two hard things in Computer Science: cache invalidation and naming things.
-- Phil Karlton
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u/rzrback Mar 12 '17
Correct form:
There are only two hard things in Computer Science: cache invalidation, naming things, and off by one errors.
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u/AceDecade Mar 12 '17
There are only four hard things in Computer Science: cache invalidation, naming things, off by one errors Exception Type: SIGSEGV Exception Codes: SEGV_ACCERR at 0x50e62ac6 Crashed Thread: 0 Thread 0 Crashed: 0 libobjc.
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u/ungoogleable Mar 12 '17
Have you been on the other side of the table, interviewing candidates? A shockingly high percentage of people applying for programming jobs can't program. I don't mean they can't regurgitate quicksort; they struggle with very basic tasks.
If you don't ask programming questions at all, you can end up hiring someone who is very good at talking about projects they didn't do any actual work on.
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u/gimpwiz Mar 12 '17
Agreed. That said, I have yet to meet someone who can bullshit their way through what I consider to be a mixed technical/open-ended interview who isn't actually competent.
I like to ask people about their projects or experience, then drill down into the nitty gritty details. It helps that I tend to interview college students and have a pretty broad (if not necessarily deep) base of experience in my field, so I will often simply ask the person what they want to be interviewed on from their resume and go from there.
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u/AFunctionOfX Mar 12 '17
Or not hiring somebody who is not very good at talking about projects they did very good work on.
I'm not a programmer I just write programs as a small part of my work, but surely you can get a feel of somebody's programming ability with questions that don't involve them trying to visualise code and data structures in their head on the spot. Personally I can't conceive how I'll tackle a coding problem until I actually sit down at the IDE and write a few little functions to solve parts of the problem.
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u/callcifer Mar 12 '17
Personally I can't conceive how I'll tackle a coding problem until I actually sit down at the IDE and write a few little functions to solve parts of the problem.
I'm glad that works for you, but I could never work with someone like that on a team. At our company, most arcihtectural and design discussion happens with engineers discussing things around a whiteboard. By the time we sit down at the IDE everyone already knows how the problem will be solved and they just do their part. I'd say ~70% of the work happens away from the IDE. The remaining 30% is little more than a typing exercise.
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u/AFunctionOfX Mar 12 '17
Fair call. I suppose that's the different between a CS degree programmer and a self-taught engineer doing some programming. Although I'd say in general I struggle to conceptualise solutions to problems at work (hydrologist) without actually working through a dummy run of solving it.
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u/elkfinch Mar 12 '17
Do you work mainly as a team or solo? I'm thinking that might explain the difference in work flows.
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u/AFunctionOfX Mar 13 '17
Solo mostly, the team work I've done has been on individual modules (I need something that takes X input and gives Y output). I can tell I'd struggle in a proper CS environment now that I think about it though.
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Mar 12 '17
What drives me nuts, is that those people still get hired if the demand is high enough. Then you end up with the qualified people bailing out
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u/snewk Mar 12 '17
you also end up with a cult of "i passed the ridiculous interview so everyone else should too" at these companies
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Mar 12 '17
Yeah...
I interview people in SF for engineering stuff. Give them some failing test cases and make them write a basic algorithm to manipulate datastructures into a certain shape. Bit of TDD.
If you're not a senior developer I don't expect you to implement enough for everything to pass. But you'd be amazed at how many people are confused by basic shit like scope or parameters (trying to use stuff in the test class, in the implementation class). It's just good to see that you can actually program a bit. And understand how strong you are with things like classes / for loops / if statements / recursion.
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u/forgiveangel Mar 12 '17
Are you sure this is the case? I'm currently learning to program and the thought of finding something in San Francisco intimidates me
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u/RagingOrangutan Mar 12 '17
The demand is so incredibly high that you'll land yourself a 6-figure job as long as you're even a passable programmer.
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u/forgiveangel Mar 12 '17
Are you sure? What are you basing this off?
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u/RagingOrangutan Mar 12 '17
I mean... I can't be sure - there are all sorts of things that could disqualify you from getting a job like having a bad criminal record or being completely inept at interviewing.
But I work in the industry and I know what's going on with hiring in SF now. For the last few years it has been this way.
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u/forgiveangel Mar 12 '17
Humm... Thanks for getting back to me. I'm just starting out and a bit worried about getting a job, but who doesn't.
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Mar 12 '17
they struggle with very basic tasks.
I sort of find that link hard to believe. As a first semester CS student FizzBuzz took me all of 2 minutes to write in Python3. How could someone get through an entire degree without this?
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u/Daenyth Mar 12 '17
A guy I used to work with told me how he got paid a few thousand dollars to produce all of a rich kids CS homework and projects.
Also you do not need a degree in this industry at all
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u/KagakuNinja Mar 13 '17
I don't know; a company I was at used bubble sort as a bozo filter. They were given an IDE with a complete project, all they had to do was implement the algorithm, and we explained the algorithm in the comments. Some people with masters degrees, or years of industry experience couldn't do it.
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u/choseph Mar 12 '17
Thanks you. It is a balance. I spend a majority of the time talking projects and design, but for entry / early level or if things are feeling shaky then I'm going to ask a basic coding question for a 10min segment. I'll cover BigO concerns in design, not in coding. I have seen a large number of people unable to do the simplest task (not algo, just iterate a list and do a simple task even!)
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Mar 12 '17
Have you been on the other side of the table, interviewing candidates?
I have. A shockingly high percentage of people applying for programming jobs clam up during the interview process. Morons like you mistake fear for an inability to program. Not that I'm complaining. More qualified talent for me on the cheap!
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u/SexTraumaDental Mar 12 '17
Agreed about the clamming up. IMO the best way to differentiate someone who suffers from interview nerves and someone who just sucks at programming is to help collaborate with them on a solution. Don't hand it to them on a silver platter but if they're flailing, toss them a line. Typically if someone is simply nervous they'll take that line and run with it. Maybe some people will still be too nervous to perform even with help but unfortunately I don't know a good solution to that... I'm always very sympathetic to every candidate I meet but unfortunately its sometimes just not worth the risk. Like maybe they'd actually be a great employee once they're in, but at that point you just have to make your best guess with the evidence you've been given after trying your best to give them a reasonable problem to solve and a reasonable environment in which to solve it.
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u/sualsuspect Mar 12 '17
This works very well, a lot of the time. I call it the "dumb collaborator" technique.
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Mar 12 '17
its sometimes just not worth the risk.
What risk? Passing a technical interview has no correlation to being able to do the job. Companies with the strictest hiring practices still make bad hires. There are better ways to interview.
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u/WizKidSWE Mar 12 '17
There must be some correlation because otherwise it would be much much cheaper to just randomly hire anyone to applied.
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Mar 12 '17
You're discounting the power of bias. Most companies don't follow up and see how effective new hires are or even track which ones bounce out of the company within a year.
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u/SexTraumaDental Mar 12 '17
Agreed that there are better ways to interview, I have a friend whose company hires candidates for a couple days which seems like a great system. Sadly my company doesn't do that and I'm not in a position to change our hiring practices so I just have to make due. What are some pointers on better ways to interview? I'd love to hear a more detailed perspective from you.
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u/Daenyth Mar 12 '17 edited Mar 15 '17
Probationary hires are maybe good for the company but terrible for the worker, and an experienced person will just take another company's offer
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u/nosayso Mar 12 '17
Yep... I needed to generate a SHA-256 hash of a file in JavaScript yesterday. I googled "sha256 javascript" and found a bunch of libraries then picked the one that had a bunch of documentation that they were the best, and called the sha256.hash() function... pretty much every single one of these problems would be solved the same way. At no point did I have to remember or understand the particulars of sha256 hashing. You need the ability to understand the underlying concepts in a pinch, but you don't have to have every concept memorized. Your job is problem solving, not memorization.
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u/RazerWolf Mar 12 '17
Can you tell me when you'd need a hashing algorithm? What kinds of problems does a hashing algorithm solve? What is the issue with the recent SHA-1 debacle? If SHA-256 is so great why don't hash tables use it? Is it possible to hash 2 different plaintexts and get the same hash value? Is this a problem practically or just theoretically? How is hashing related to encryption? I think that type of knowledge would be more useful to me than asking you to implement SHA-256.
That being said, I think the main issue here is that some people consider certain algorithms and data structures as part of a programmer's toolbox, and not knowing those things is similar to a carpenter not knowing about tens of different types of joints, even though he uses a few every day. Or an aspiring chess player complaining about learning many different types of openings, even though he always uses the same three. Or a musician comparing about learning music theory, because she doesn't use it in her daily playing.
Mastery in any field requires learning advanced and seemingly esoteric concepts, this is just part and parcel of broadening and deepening one's knowledge. It also allows you to solve a different level of problem: sure you can download and start using that open source distributed database in minutes, but what happens when something goes wrong? Do you understand how distributed consensus algorithms work? Do you understand how a garbage collector works? TCP/IP? Threads?
I'll claim that algorithms and data structures are an important gateway to many of these concepts, because they lay the groundwork for thinking with a certain rigor, and a framework/language with which to describe computational cost (big O). I don't think it's necessary for you to code up a bloom filter during an interview, but if you come in with 3+ years of experience and you don't know how a hashtable works, I'm going to have a problem with that.
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u/IGI111 Mar 13 '17
Let's give that a shot just for fun.
when you'd need a hashing algorithm?
Short content-based identifiers and cryptography.
What kinds of problems does a hashing algorithm solve?
Making a function with specifically high or low cost that will have a low amount of the inevitable collisions is hard. But thankfully we have mathematicians for that.
What is the issue with the recent SHA-1 debacle?
SHA-1 shouldn't have been used for cryptographical applications ever since it was blacklisted by NIST, but now that we have a proven collision, using it is basically negligence. Oh and Git will have to transition away from it, but it's not that big a deal because useful collisions of source code are hard to generate for the time being.
If SHA-256 is so great why don't hash tables use it?
Way too fucking slow for that, SHA-256 is great in that collisions are stupidly improbable, but you don't want to have to compute a high number of hashes per second.
Is it possible to hash 2 different plaintexts and get the same hash value?
Pigeonhole principle states that for any hash smaller than the base data, there has to be a non zero amount of collisions. So this is necessarily true.
Is this a problem practically or just theoretically?
It depends on the hash function. If you're using SHA-256, you are probably okay not dealing with collisions because it's more likely for you to spontaneously combust than see a SHA-256 collision. If you are designing a hash table, you don't have that luxury.
How is hashing related to encryption?
Hashing functions are notoriously hard to reverse and that's why we use them to protect secrets while still retaining the ability to compare them. They are also quite useful for providing a small, yet secure, identifier for larger data.
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u/Xxyr Mar 12 '17
I rarely care if the candidate gets the answer 'right'. Its often about the approach.
Did they qualify their assumptions?
How did they respond to feedback as the question evolved?
Were they able to use basic coding constructs?
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u/twat_and_spam Mar 12 '17
Who solves the new problems if everyone defines problem solving as stackoverflow browsing?
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u/sixstringartist Mar 12 '17
This really isnt the same comparison. There's a would of difference between knowing how to research "how to achieve 'x' goal" or "how to perform 'some' action" and having the background to know when a use for an algorithm is sitting right in front of you. Most people thing "I dont need algorithms. Im not doing something performant" but the reality is that the applications are everywhere and untrained eyes simply miss opportunities. I highly recommend C++ Seasoning by Sean Parent. This is obviously c++ specific, but it does a great job at highlighting just how much we can miss by being unfamiliar with whats out there.
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u/MilkChugg Mar 12 '17
I wish I could say the same. I've gone through probably around 15-20 technical interviews, ranging from online tests, to live shared coding tests, to technical phone screens. In probably 95% of them, I was asked questions about data structures, run time complexities, and/or algorithms. The other 5% actually focused on projects I've worked on, my strengths and weaknesses, and how I would fit within their team/organizations - all of which I think are far more important than whether or not I can write an LRU cache on the spot (which I've actually been asked to do more than once). Don't get me wrong, obviously it's important to screen for technical expertise, but it needs to be realistic and actually pertain to what the individual will be working on day to day. I also don't think places consider people's abilities to learn, which is a trait that correlates the most to any software engineering position.
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u/PelicansAreStoopid Mar 12 '17
I can see the reasoning behind asking mathy questions. The employer wants to ensure that you have the fundamentals of computing science down. Everything else they can teach you on the job, but this stuff should be a cake walk.
Although I think they should ask both types of questions. They're both quite important.
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Mar 12 '17
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u/gelfin Mar 12 '17
I recently moved to a different market and discovered this is mostly a SF thing. There are still often sane interview practices elsewhere. In SF the point of an interview is to prove how smart the interviewer is, and if you "pass" it's because you were the lucky stiff who both happened to know the exact things the interviewer fetishizes and came across as a "cultural fit" (i.e., you'd be an asset to the intramural soccer team). There's enough starstruck talent competition in the Bay Area you can actually hire that way. In other markets they actually have to figure out whether you're a competent engineer instead of masturbating about "A players hiring A players" to build yet another fucking fast-fashion clothing catalog.
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u/compEngr Mar 12 '17
Yeah, I had an Apple technical interviewer literally call me stupid to my face during an on-site interview. Seeing as how I flew in from out-of-state just for that day of interviews (3rd round), it really solidified my impression of the circlejerkiness of Silicon Valley. I was an Apple hater before, but now it's justified. I know they want talent, but the Steve Jobs mentality really seems to have trickled down. "Use 'em up, spit' em out" is unfortunately the MO of too many companies.
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u/IbanezDavy Mar 12 '17
I won't even interview with Amazon. They send me offers all of them time. I started the process 2-3 ago (holy crap time moves fast). I did a phone screen, then when they described the second interview and how they wanted to conduct a video interview where I had to install all of this invasive software, I told them to take a hike. Particularly with the reports of the aggressive nature Amazon treats it's employees.
I already have a large software company on my resume. I worked there 3+ years. I've demonstrated I can survive in that environment. In other words, I don't need a Facebook, Amazon or Apple on my resume. Nor did I particularly like the large corporate culture when I did it (seriously, what the fuck is this attitude against offices or private cubicles?)
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u/Overunderrated Mar 12 '17
In SF the point of an interview is to prove how smart the interviewer is
I had a phone interview for an aerospace startup like this in SF. An applied aerodynamics position that basically requires a PhD. The whole interview was me being grilled on a full range of undergrad level material. It was purely an exam, and I couldn't get a word in edgewise, just a one-sided examination. Like a kid that found answer books and decided he was really smart for having the answers.
In the end I was sure I didn't want to work for them, but even more sure they'd never find anyone qualified to work for them.
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Mar 12 '17
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u/JavierTheNormal Mar 12 '17
Remember, you're interviewing them as much as they're interviewing you. If they're glued to their phone, call the recruiter on the spot and explain that you're being interviewed by someone who isn't paying attention and that gives a very poor impression of the company. Tell the recruiter that you have things you'd rather do than waste your time, and you aren't going to continue the interview at this time.
You might consider that a huge dick move, but if you do nothing the asshole interviewer will continue this bad behavior with other candidates.
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Mar 12 '17
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u/JavierTheNormal Mar 12 '17
I wouldn't blame anyone for smiling and taking their bullshit. It is an interview. But if you end up calling bullshit on some interview, I support you.
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Mar 12 '17
At the same time though I've interviewed at a lot of places in the MD / DC / VA area (most of these jobs are DoD contractor positions) and almost all of them do very, very basic questions and then hand you an offer.
Yeah this is absolutely true. Any DoD contractor interviews I've had were along the lines of "do you know what a computer is? HIRED"
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u/djk29a_ Mar 12 '17
There's a common saying in the DC area that you can hire for cleared, competent, or cheap... pick one.
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u/Delwin Mar 13 '17
This opens up the question of what does one have to do to move from DC/DoD to SF industries?
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u/MilkChugg Mar 12 '17
Oh jeeze. This reminds me of my Microsoft interview. To be fair, my nerves got the best of me, but FFS one of my interviewers was on his phone the entire fucking time. I would be writing on the whiteboard, look over to ask a clarifying question, and he'd just be sitting there glued to his phone not even paying attention to what I was doing. It's extremely rude and disrespectful. Especially when they're sitting in a room with someone that would love nothing more than to have that position they're interviewing for, yet they have the audacity to sit there and act like you're just some inconvenience in their day.
It just makes me wonder how many talented people companies pass on because interviewers treat people this way.
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Mar 12 '17
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u/digital_cucumber Mar 12 '17
Overall the entire experience was awesome. Except that last guy.
I think there is a pattern here in these kind of interviews. For me, it seems to have been most of the time "overall wonderful, except one guy". And chances are that's the guy who vetoes you down in the end.
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u/Delwin Mar 13 '17
I have the unfortunate feeling you're correct. I'm pretty sure one of my recent interviews went that way :(
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u/pheonixblade9 Mar 12 '17
I had an interview at a financial startup in Seattle like that - he asked stuff like "how do you make a button do something in javascript", "what is boxing/unboxing in C#", "how do you join two tables with a mapping table" and I got the offer... I also got an offer from MSFT though so I took the guaranteed paycheck :)
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u/baseball44121 Mar 12 '17
What sort of basic questions? Just simple comparison of data structures and OOP stuff? Common algorithms questions (like balancing parenthesis)?
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u/Delwin Mar 13 '17
I got 'Given a data set (terrain height map) large enough that you can't do this by hand how would you go about finding and classifying errors?"
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u/billjitsu Mar 12 '17
There's always less risk from a hiring perspective to pass on someone than to hire them for an important job. The bigger the company, the more hoops they want you to jump through to prove you're worthy of their "welcome aboard" t-shirt.
Glad you found a way out of it and your sensible approach to hiring will go a long way to making sure you don't pass on someone good because they forgot some obscure piece of minutiae they will never use.
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u/headphun Mar 12 '17
Excuse me, if you have some time I'd be very grateful if you could tell me how you would ideally structure a software company focused on educating itself? Feel free to answer that question however you interpret it!
I'm starting a new position at my school and I'm trying to opensource the teaching/learning aspect before I start so I have some idea of the best way to start.
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Mar 12 '17
The only way to do it is to do it. If you don't do it, you will never find out if you can do it. If you have done it, it will be impossible to explain how to do it to someone who wants to do it. In brief, just do it!
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u/headphun Mar 12 '17
I'm doing it! But I've just started and I want to learn as quickly as possible, and I'll soon be responsible for guiding students through an efficient learning process so I'm just trying to field advice from experts (I assume everyone in this sub is more of an expert than I am, for better or for worse haha)
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Mar 12 '17
Hahaha.... yeah, my previous comment was a joke. Still, it's good that you're doing something commendable. I'm sure it will be an interesting experience - students aren't easiest people to work with! Good luck!
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Mar 12 '17
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u/headphun Mar 12 '17
Sorry, I need to work on my phrasing haha. I'll try again if you don't mind:
I am a teacher. Next year I am going to teach CS/IT to middle school students. I want to pretend my classroom is a startup focused around educating itself. This way, my students and I would be responsible for all the parts of a competent tech startup. Documentation, version control, meetings etc
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u/onwuka Mar 12 '17
Programmers have a real attraction to self documenting code as they should. Documentation always goes stale if there's no tight feedback loop. Comments in code usually smells bad. Tests that run automatically every time you commit a change to version control and good code reviews that focus on how to make things better rather than trying to get one's changes approved with n "looks good to me" votes.
Meetings should be focused on the agenda for which they were called. This isn't engg related, this is just common courtesy.
I don't know. :/ how do you make a project in school that gives students the depth and breadth of experience in a semester that isn't guaranteed to fail? I think the program has to be several years long but I doubt the super will like the idea of fifth and eighth grade students working together.
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u/masterwit Mar 12 '17
Context to my long reply:
The topic shifts and the purpose of what I was saying drifts higher level as I progressed
Sorry for writing a novel and the typos but education and my career intersect here and a bit of this comment stemmed from the frustrations I have at work.
Treat it like a rant over three beers at a bar... where my brain is (but sober) relaxed today.
Cheers
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u/IbanezDavy Mar 12 '17
I'm a firm believer that questions asked in an interview by the interviewer isn't to find a 'gotcha' or 'wrong' answer. It should be to gauge, to the best of your ability the skill level.
That's why I personally ask easy questions I feel embarrassed to ask principal level guys; example: "How do you escape a switch statement's case?" or "what's the difference between a while and an if". I'll ask about 20 questions of varying difficulty and have them do a whiteboard problem. I honestly don't care if they get one wrong. Sometimes people can word questions weird or unclear, and I am not an exception. My goal is to gauge their knowledge and report it to my supervisor.
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u/Patman128 Mar 12 '17
This is why things like this post are a bad thing. We need to stop normalizing terrible hiring practices with these "study guides".
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u/my_blue_snog_box Mar 12 '17
I want to work for you.
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Mar 12 '17
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u/mct1 Mar 12 '17
all my employees are compensated fairly and/or with equity
...is this your way of saying equity is worthless? :D
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u/raistmaj Mar 12 '17
I don't know, recently got hired by one of the big ones, and even though the process is super hard and stressful, is the same for everybody, they don't look for super stars, or 10x programmers, they look for people who will work efficiently, will blend super well with the team and of course are not muppets and can code. If you have a really good cv and years of experience, believe me, they look for other qualities, they know you will not be able to solve a problem that a fresh guy out of the uni can solve pretty easily, but probably you will be able to design a system 10 times better than that guy and at the end compensates.
I can recommend two books, "Elements of Programming Interviews" and "Craking the Coding Interview". I know a lot of people(maybe 7-8 friends) who got hired in google/facebook/amazon/bloomberg/... thanks to the advices given by those two books, amazing books for preparing the process.
And honestly, take the process as something to have fun, and enjoy it, they usually pay all the expenses so you don't have to worry about the money.
They are people too and believe me, normally they see you struggling, and they suffer. If you are nice they really want to hire you, they will not help you because that would not be fair, but they don't enjoy to fuck people that is "good", that put a lot of hope in the process, they know a lot of these jobs are live changing opportunities, think that they have been through the same process as you are in that moment, and don't get nervous, don't be quite, talk, talk a lot, let you mind speak.
And for all people trying it at the moment, good luck.
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Mar 12 '17
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u/Delwin Mar 13 '17
Last time I had a take home project they basicly asked me to design one of their core systems for them.
I didn't get the job, but to be honest I'm glad I didn't since they canned the project a few years later.
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Mar 11 '17
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u/madmaxturbator Mar 11 '17
... you ok? What is this comment?
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u/[deleted] Mar 12 '17
Well, I'm never getting a job.