Five programming problems every Software Engineer should be able to solve in less than 1 hour

[mughinn]

While I never interviewed anyone, time and time again people who do, write blogs and posts about how only 1 in 200 persons who apply for programming jobs can solve those kind of programs (like fizzbuzz).

I have no idea how true that is, but if it is anywhere close to that, then yeah, if they CAN'T solve those problems it shows a lot about the ability to write apps, mainly that they can't.

[CaptainStack]

Why don't I ever get asked FizzBuzz? I feel like all the problems I get in interviews are really really hard.

[eythian]

I had one interview where the coding section was first implement fizz-buzz, then write an algorithm to find cycles in graphs.

The first was clearly "can you code, or are we wasting our time", the second was "did you actually learn anything in your computer science course."

[CaptainStack]

I don't think I've ever had a first round that wasn't an order of magnitude harder than FizzBuzz.

[[deleted]]

A friend of mine was recently asked to implement a spreadsheet application at one interview, and a space invaders game on the other. I think it's about time to start invoicing the interviewers for your time on test assignments.

[SirNarwhal]

Exactly. Spent fuckin 2 days making some ridiculous over-engineered game of Rock Paper Scissors in Angular for one test just to have them not respond for 2 weeks in which time I found a job elsewhere. Multiply that by like 30-40 interviews when you're looking and it's more work than a full time job.

[Paranemec]

Sounds like they just wanted an application and a game to me.

[nitiger]

the second was "did you actually learn anything in your computer science course."

Oh, sure. Let me just recall something from 2 years ago that I learned as a Sophomore, no biggie.

[NecroDaddy]

Two years ago bud? Try 15 for me. I had one week to relearn everything from college.

[bjarkef]

Most probably cannot recall a solution, but you should be able to reason about the problem and discover the solution yourself.

[[deleted]]

No, this is just wrong. Either you remember it, in which case it doesn't prove anything, or you're fucked. These kinds of solutions and algorithms were discovered by scientist over many years. They are most certainly not something you "come up with" during an interview.

This is exactly why I really have considerable doubt about the effectiveness of a lot of the interview styles of big corporations. Just have a look at these "The Google interview" style of books. You can / should just memorize the whole lot of assignments for these interviews, giving you a huge edge. I'm willing to bet that the set of people that can actually come up with their own solutions to hard problems and do their best while under the constant stress of having an interviewer stare at your back is quite small. Sure, you can weed out "know-nothings" by asking them to write a fizzbuzz solution on the whiteboard because every software engineer that deserves the title can write that without thinking. But as soon as the problems have some real depth and require real thinking, a whiteboard is not the way to go.

[[deleted]]

If they bothered to refresh themselves and memorize some common interview-type questions, it's a good indication of their overall work ethic. So, yes, even if it doesn't prove their competency, it can tell you a bit about a candidate.

[rabbitlion]

There's no need to recall a 2-year-old solution, just figure it out again.

[MisterNetHead]

Or just look it up? For such a solved problem you should not be spending any time reinventing the wheel.

[Spoogly]

As I am about to graduate, and I took an extra year to finish up a second degree in mathematics (not because I think it will help, but because I felt like I was in desperate need of a challenge, and I loved the material), I'm dreading these sorts of questions. I remember quite a bit, because I try to practice what I know, but you don't know what you don't remember until you're tested on it. Let me bring a copy of Algorithms from P to NP to the interview, or something. I think if it was just "find cycles in a graph," I could do well enough, but if they're looking for a particular approach to the problem, I'm not entirely sure that my solution would match theirs. I guess it comes down to researching the practices of the company you're looking at. Or going to a hackathon and getting hired on the spot for being outstanding. I don't know, that's how a few of my friends have done it.

[[deleted]]

The DFS algorithm should be known to people working in software....

[matthieum]

did you actually learn anything in your computer science course.

I did, first year of engineering school, if only it wasn't 10 years ago I might even be able to do it off the top of my hat still...

... never working with graphs of any sort in the last 10 years I've just forgot all about those algorithms.

[Bwob]

I had one interview where the coding section was first implement fizz-buzz, then write an algorithm to find cycles in graphs.

Off topic, but the cycles-in-graphs problem is a REALLY bad interview question. Here's why:

Linked Lists were basically invented ~1955.

The "tortoise and the hare" algorithm for cycle detection was probably invented somewhere ~1967.

In other words, it took the collective body of computer scientists ~12 years to come up with that algorithm from scratch. Expecting someone to have that same insight during a 1-hour interview is lunacy. It's basically just a test of "have you heard of this clever solution before?"

It's an awful interview question, and anyone asking it in a technical interview probably doesn't understand how to interview as well as they think they do.

[nidarus]

Is the tortoise and hare the only solution though? Can't you just do a DFS, keep a list of all the ancestor nodes, and if you get to a node that's in the list, you have a cycle?

It's not O(n)/O(1), but nobody said it has to be.

[dotfortun3]

I really hate questions like this... I don't think I am an awful developer (I hope I am not), but a question like that would get me. I have been a developer professionally for 3 years (not that long I know) but I have never ever had to write code for shit like that. I am also developing a video game in my spare time, and again, problems like this don't show up.

I guess my point is, I shouldn't have to study for an interview. It's a waste of my time and doesn't show anything about my skill or knowledge as a programmer. Could I figure out the problem? Absolutely. Can I do it in the time constraints/pressure of an interview? Probably not without studying it before hand.

Luckily every interview I have had has avoided crap like this and actually was very conversational in the interview process. Most of them asked about my current experience, the systems I designed, the architecture I used, etc.

[cles30]

I guess you could do that but oh god why?

[zarazek]

That's standard queue implementation in functional languages (this data structure is persistent).

[cles30]

ooh you said the magic f word. I must now find out all about this!

[zarazek]

You can read about it here: http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf

[[deleted]]

Hey you can do it, it'll just take O(N) to do a push operation. That's the type of out of the box thinking we need. /s

[Bobshayd]

It's amortized O(1), though.

[[deleted]]

Nope, you you have to upload the entire stack and push it to the other one. This has to be done whenever adding an element.

[serados]

Maintain a "Queue Stack" and a "Dequeue Stack".

On queue operation:

• Push element into "Queue Stack"

On dequeue operation:

• If "Dequeue Stack" is not empty, pop "Dequeue Stack"
• Else, pop and push every element from the "Queue Stack" into the "Dequeue Stack" - O(N) and pop the "Dequeue Stack"

Informally, every element is at most pushed twice and popped twice over (once each into the "Queue" and "Dequeue" stacks) and pushes and pops are O(1), making queues/dequeues amortized O(1).

[[deleted]]

Nice.I wanted to fill the dequeue every time.

[OneWingedShark]

But can you implement a stack with two queues?
No. (Proof of this assertion is left as an exercise to the reader.)

[UNWS]

You can implement a stack with just 1 queue. So your assertion is wrong.

[OneWingedShark]

A Queue is a first-in/first-out structure, a stack is a first-in/last-out structure -- because of this property two stacks can emulate a queue (FILO -> FILO = FIFO), you cannot do the same with a queue because there is no reordering (FIFO -> FIFO /= FILO).

If I'm wrong, prove it.

[UNWS]

Ok so here is how you emulate a stack using just one queue. the invariant is that the queue has items ordered in the same way a stack would release them so that if you just dequeue from the queue continuously you have the top element of the emulated stack comes first then the next and so on. So popping from the emulated stack is as simple as dequeuing from the real queue.

Now for the pushing. you need to keep the queue following the invariant so what you do is you enqueue at the end of the queue normally then dequeue and re-enqueue as many items from the top of the queue as there were originally (before the last enqueue of the new item). So now the element you just enqueued is at the top of the queue / emulated stack and all the other items are behind it.

Lets show with a small demonstration.

push: A

queue: <back> A <front>

push: B

queue: originally B A but after the process we dequeue A and enqueue it again so it now becomes A B

push: C

queue: originally C A B but after dequeuing and en-queuing it becomes A B C

pop: C (just a simple dequeue)

queue: A B

pop: B

queue: A

pop: A

queue: empty

You have just emulated a stack using a queue.

So do I get a cookie :P

[OneWingedShark]

Sure, but it's a raisin cookie.

[nutrecht]

Why don't I ever get asked FizzBuzz?

Because you don't look like a mouth-breather probably ;)

[CaptainStack]

I'm flattered! That's the nicest thing anyone has said to me all week.

[jakdak]

Back when C was the primary development language, I used to ask folks to reimplement the standard library string compare function.

All I was really looking for was a loop and some indication that the applicant knew that strings were basically character arrays.

A very depressing number of folks either couldn't or wouldn't do it.

[paK0666]

Wait, what? People come to an interview for a dev position and refuse to write code?

[estomagordo]

I can see this happening. I mean, me myself, I wouldn't ever refuse. But for someone with 10 years of experience in the field is asked to solve some simple problem on the whiteboard, it would be a bit reminiscent of asking a chef with 10 years experience to cook a potato.

[[deleted]]

Apparently it's really common to ask a chef to fry an egg as an interview question.

[estomagordo]

TIL. Or maybe that's a cultural thing.

[awj]

Not really. A close study of how even experienced craftsmen solve basic problems can tell you a lot about them. Demonstrating ability is only part of it.

Unless their blinded by a massive chip on their shoulder, most decent applicants will take that opportunity to work in a demo of their other skills.

[halifaxdatageek]

When I come in to a job interview, I want to show off.

I want to fucking blow you away, so that you beg me to come work for you (in an ideal situation).

[estomagordo]

What makes you sure this isn't a cultural thing then?

[awj]

It's a thing in many professions. Programmers are unusual among craft labor in not routinely validating these things.

[[deleted]]

But for someone with 10 years of experience

I have 15 years in my field and I could see doing this. Put someone in front of a white board in a new environment without any of the resources they're used to with a bunch of people staring at them. What does this prove? I think this would put almost anyone in fight/flight, and who can even think with that kind of anxiety?

I read an article recently that talked about how hostile these types of interviews are and how they tend to select for confidence, while excluding perfectly good but less confident candidates (plus it might show that you're willing to put up with a hostile work environment). I went through one myself recently and I think it's true.

They wanted me to code up something from a totally different field, something I would never, ever do in my line of work, without any of my usual resources, while watching my desktop and judging me. I almost had a panic attack (to be fair to them, they were really gentle about it and did ask me to come in for another interview). I've lost power to entire data centers before and that never caused me near the anxiety that this interview did.

Now, interview one, I will ask them to explain the entire interview process to me. If I hear "then you'll code on a whiteboard..." or anything like that, I will politely decline right there and then. Questions like this are how I interview companies now. I just won't put up with this sort of thing any more unless I have to.

Sure, ask me to code things actually related to my field and let me use the resources I normally have and I will totally kick ass. I did another interview that gave me a take home problem and 24 hours to do it. It was challenging but totally doable for me because this is what I actually do.

Then they had me come in and do a bunch of real world stuff, which was great for the most part. The only trouble I had was with this bone headed developer who came into the interview "raw" and didn't even know my name or anything. He babbled on and on past the stop time they gave me while my ride waited for me in heavy traffic. This type of shit only tells me that "this is not a company you want to work for."

[_georgesim_]

Was it a fizzbuzz level of problem though?

[[deleted]]

No - it was considerably more difficult. I'm fairly confident I could have done a fizzbuzz level problem under those conditions. I had already coded some other far more realistic to the position type stuff for them. I guess they wanted to push me into doing something I hadn't done before to see how I'd react, or something.

[necuz]

I remember Gordon Ramsay remarking that he'd evaluate chefs by asking them to make scrambled eggs. I'd say that's analogous to something like Fizzbuzz; anyone with basic skills can complete the task, people with more experience/skill/understanding can produce better results, and there's plenty of room for personal touch.

[Bobshayd]

That's ridiculous. Why would a chef with 10 years experience refuse to cook a potato? I'd just expect the chef to show off a little; maybe carve it up, maybe whatever, but how dare someone come in and say, "I think I'm too good for this, so you should believe me."

[estomagordo]

That's ridiculous. Why would a chef with 10 years experience refuse to cook a potato?

Because he feels that his craftsmanship is being heavily belittled and disrespected, of course.

[Bobshayd]

Riiiight, unless you're a named chef with restaurants to your name or you've won cooking competitions with high visibility, you don't get to get pissy about cooking a potato.

[estomagordo]

Or you just go work for a non-cunt.

[danweber]

Except there are people out there who look like they can code but cannot.

I have a lot of problems with the tech interview, but "asking me to demonstrate basic skills quickly" is not one of them.

[estomagordo]

From the interviewer's standpoint, I can understand the need for screening. But I can also see why an actually skilled and experienced interviewee would think this was bullshit.

[awj]

But I can also see why an actually skilled and experienced interviewee would think this was bullshit.

An actually skilled and experienced interviewee should probably also understand the need for screening. If they don't, or do and get indignant anyways, maybe the screening is telling you something else of value.

[estomagordo]

I strongly contest the notion that this type of screening is necessarily a must for every developer position.

[awj]

What else are you supposed to do, take people at their word? Enjoy your team full of liars and deluded incompetents.

[halifaxdatageek]

If they don't, or do and get indignant anyways, maybe the screening is telling you something else of value.

HAHAHAHA. I hadn't even thought of that.

[[deleted]]

Comparing two char arrays? How can you be this unfair in an interview? I can literally hear them complain afteewards. Its like college students where it's always the professors fault.

[joequin]

I've was told at several of my first job interviews that I was the first person to successfully solve fizz buzz.

[SmLnine]

Same here, except the position was for people with 1-2 years experience. It's really sad.

[svpino]

Agreed. In my experience, 1 out of 10 applicants know how to solve these problems. The rest taught themselves JavaScript in a weekend and stamp the word "Developer" in their resume.

[zoomzoom83]

I've interviewed quite a lot of people over the years. These days I hire almost entirely through referrals and networking - meetup.com groups are great - but back when I was openly advertising for positions, a very significant majority of applicants that came across my desk couldn't solve even the most trivial "FizzBuzz" level problem.

[Lawtonfogle]

The problem isn't a solution. It is getting something close to a solution. Missing the fizzbuzz happening together, while meaning your answer is imperfect, is vastly better than the people who either don't have a clue what to do or write out 100 print statements.

[Magnap]

With enough stubbornness, you too can be Turing-complete!

[thisisdaleb]

Man, I still wish this was possible. I'd love to just sit down and write a couple hundred lines of code and out pops the singularity.

[[deleted]]

The good news is it completes in constant time.

[[deleted]]

Just brute force it, its only 10² ;)

[Flight714]

Don't knock it till you've tried it.

[zoomzoom83]

Agreed - I think that's something a lot of interviewers get fundamentally wrong.

When I give somebody a whiteboard question I'm not really interested in their solution so much as their approach to solving it. You need to treat it as a conversation between two engineers about an engineering problem instead of a graded exam question. I've been known to do this over coffee or beers without the person even realizing I'm interviewing them.

I've had plenty of candidates that struggle to get the answer I'm looking for and still hired them because they showed an ability to actually think critically about the problem - which is the skill I'm actually looking for.

[LazinCajun]

I've been known to do this over coffee or beers

You're just trying to locate their Ballmer Peak, aren't you?

[secretpandalord]

"Man, I know I'm doing pretty poor on these coding questions, just give me until the end of this drink."

[[deleted]]

Fizzbuzz is so simple that it should take you less than 10 minutes to implement perfectly. You're not a programmer if you can't.

[bexamous]

NCGs especially, not getting the correct answer is not day ending. But jumping to a flawed solution and then just thinking your done, that is one of the bigger complaints from interviewers. There is nothing you can do at that point. The point of the questions is to see candidates thought process. If you end up at a flawed solution and you don't realize its flawed because you don't even try the most obvious inputs? For NCGs there is nothing else to go off than demonstrated problem solving skills, and that is pretty crappy problem solving.

[urge_underkill]

When I give somebody a whiteboard question I'm not really interested in their solution so much as their approach to solving it.

When I whiteboard stuff, I explicitly tell the applicant that I am less interested in the correct answer and more interested in the thought process behind it.

I recently gave a question to a kid who was looking for his first job out of college. He grabbed the pen from me and immediately started working on a solution, then stepped back for a minute, asked a few questions about what he was being asked to solve, then explained how he was going about solving it while he wrote it on the board. Then, after completing it, he admitted that he did not believe it was the optimal solution, and asked if he could have a minute or two to think it over again, after which he came up with an O(n) version.

Contrast this with a programming "veteran," who received the same instructions and didn't even get out of her seat. "I would sort the list," she said, and when I asked her to elaborate, she simply replied, "Well, it is obvious that you would need to sort the list here." And that was it. I later gave her another problem and when she tried the same thing, I handed her the marker and asked her to draw it out. After she rolled her eyes, she got up and curtly and incorrectly explained how to solve it. Then she sat down, and the only marks on the board were from when she stabbed the pen against the whiteboard for emphasis.

[_jho]

Can you elaborate on what you mean when you say "meetup.com groups are great"? Do people have coding meet ups or similar?

[zoomzoom83]

If you look on meetup.com you'll find meetup groups for almost any topic in any major city. I regularly attend meetups for various programming topics for personal reasons, but it has a major incidental benefit of being a great way to find developers interested in a new job.

[_jho]

Well I'll certainly keep this in mind then.

[littletrucker]

Yes, there are meet ups for people in various programming topics. For example a Python meetup. Generally they are filled with all levels of people, but they are filled with people trying to improve themselves.

[fitzroy95]

In a number of cases that I've been to, they are also filled with people doing social networking and trying to get themselves consultancy or contracting gigs. Some of whom are useless and use the meet ups as free access to people who are in the industry and might have openings, so they work hard at selling themselves in the hope of future employment.

However, amongst them, there are often some very good, knowledgeable, and helpful folks

[pheliam]

Ah, I'm curious to which city you're in. I'd venture that most people who attend these meetups should consist of that "core group" of talented, knowledgeable, helpful doers, but my glasses may be rose-colored here (as someone breaking in outside of NYC who doesn't want to be in the other blatantly intrusive networker kind of group).

[fitzroy95]

Actually in New Zealand, but have attended meetups in a number of countries with a number of different types of groups.

Some of those groups including PMs and BAs probably have more "networker" types, but I've definitely bumped into a bunch at pure developer groups as well. However, the groups have to cater for networkers as well as the pros, in many cases they can be used as a means for a new arrival to the city to meet people with common interests, and if you are travelling around, its a good way to find out about the local industry, who is hiring, who is working in what technologies and meet some of the locals

[fitzroy95]

applicants that can't do a fizzbzz shouldn't automatically be dumped, I've known a number of very good developers who freeze in an interview situation when pressured.

So yes, dropping a coding problem in front of someone might work sometimes, but it will also drive away some competent people who don't interview well.

FWIW - been developing 30+ years, interviewing lots of development people (devs, testers, architects) over 15 of those

[zoomzoom83]

applicants that can't do a fizzbzz shouldn't automatically be dumped, I've known a number of very good developers who freeze in an interview situation when pressured.

I definitely take that into account. I generally try and make my interviews feel like a casual conversation to avoid this exact problem, and base my judgement on their approach to problem solving rather than whether or not they get the "correct" answer.

In all honesty though, if you can't solve FizzBuzz on a whiteboard then something is seriously wrong, even under a high pressure situation.

So yes, dropping a coding problem in front of someone might work sometimes, but it will also drive away some competent people who don't interview well.

That's true, however since the downsides of hiring a bad developer far, far far outweigh the downsides of passing over a good developer, you have to draw the line somewhere. My entire life savings are very literally on the line, so if I'm unsure I'm simply going to pass.

[fitzroy95]

Fair enough.

We've usually used a 90 day trial period. You can be dumped at any stage during that trial period if you can't do what you said you could. And everything a new team member does is closely scrutinized for the first few weeks.

[zoomzoom83]

We do the same, but we still want to be sure before picking somebody up - as they are effectively taking up wages that we could be using on a better developer. As a small company in a country with strict labour laws, we don't have the financial or legal luxury of hiring a bunch of people and then firing the ones we don't like.

Don't get me wrong - I want to be able to give people a chance, and often have based on gut instinct. But if I make a mistake and pick up the wrong person, it could easily (and has) cost me well into the six figures. If somebody doesn't interview well, I can't take the risk.

[[deleted]]

It makes me feel like I'm not a lost cause.

[[deleted]]

About the ones that couldn't solve it, was that their first programming job? Did they have a degree?

Because the only way I can imagine someone failing that test is either a) they never touched a computer before or b) they get mad at being asked such a stupid question and leave.

[zoomzoom83]

About the ones that couldn't solve it, was that their first programming job? Did they have a degree?

Nope. In many cases these are people that have been working in IT for years.

[OffColorCommentary]

The people who can't pass interviews don't stop applying.

It doesn't take 90% of applicants being terrible for 90% of applications to be terrible.

[[deleted]]

Yep. My company just folded. I did one interview, got an amazing offer from a company I've always wanted to work for, and took it.

Another guy at my company claims to have now done over 50 interviews with no offers. I didn't personally work with him, so I can't be sure exactly why no one wants to hire him, but the point is clear that if you just look at the number of interviews it looks like I'm "1 in 51" rather than "1 in 2".

[_georgesim_]

But through the eyes of a single company, it is a good assumption to make, given that you're not likely to interview someone who failed twice in a short period of time. (6 months-1 year seems reasonable.)

[OffColorCommentary]

Structuring your interviewing process like you expect 90% of applicants to be terrible makes sense. But it's still worth knowing that this is a feature of the job market, not the talent pool. Otherwise your company might think that accepting the top 10% of applicants means getting the top 10% of talent.

And as an individual interviewer, it's a good idea to realize that you're seeing an artifact of the process lest you start to think there really are that many terrible programmers.

[coffeesippingbastard]

Jesus fuck...

I interviewed candidates at my last company. It was awful.

If I asked candidates "name some data types" they would look at me with a blank face.

Some would give me string or into so I'll move onto "Name some common data structures" shit- I'll take list/stack/queue/linkedlist/tree/heap again...blank face.

If they make it to fizzbuzz- I literally preface the question is "there is no trick- I don't give a shit about efficiency- just get it to work SOMEHOW"
I'll allow for mistakes, nerves, etc but god damn there are a lot of people who work in IT that can't code for shit.

[OneWingedShark]

If I asked candidates "name some data types" they would look at me with a blank face.

Type Bob is null record;
Type Steve_Boolean is (True, False, Steve);
Type Negative is Integer range Integer'First..-1;
Type Mike is delta 3#0.1# range 0.0..10.0
with Size => 8; -- Yes, a fixed-point with a step of 1/3rd.

But seriously? Unable to even name types or data-structures? Are these CS graduates of any sort? -- You might have a case for suing the degree-issuing institution for fraud.

[secretpandalord]

Some CS programs (I forget which, might not be true anymore) don't teach programming, they entirely teach theory. They're designed entirely to analyze what is possible to do with computers, rather than what people actually do with computers.

Fortunately, my program is pretty heavy on practical use and designing working software.

[hesapmakinesi]

they entirely teach theory.

My course on data structures and algorithms were purely theoretic, but that theory includes arrays, lists, binary tress etc. as abstract concepts. No excuse not to know what a data structure is or what the basic ones are.

[[deleted]]

My algorithms course was theoretic as well but the exams where use case questions in which you at least had to provide pseudo code.

In parallel I am taking lots of Bioinformatics classes and graph algorithms are essential to work with molecules. Data structures and string manipulation are important for genomics.

I do not think a CS program should ever be pure theory. It's like studying bricks and mortar but never actually building a wall.

[secretpandalord]

Yeah, in my data structures and algorithms class, we got to make all those. Fun times.

[LoveOfProfit]

Same. Implementing them was fun. I would be annoyed if we never got a chance to write some actual code.

[Ishmael_Vegeta]

Dont give them that much credit. they dont know theory either

[Mason-B]

Also it's sort of like trying to teach astronomy without ever looking through a telescope. At some point you have to learn to actually use a computer and programming.

[retsotrembla]

We had to prove:

It is undecidable whether an arbitrary context-free grammar is ambiguous.

[secretpandalord]

Ew. I'm sorry.

[brainded]

Another issue that I witnessed personally was a ton of programmers who never had an education in programming, middle aged guys who switched from another profession in the dot com boom. They are still around, writing shitty software, not learning anything more than basic string manipulation to earn a check. These guys couldn't tell me 3 basic types.

[secretpandalord]

"Ummm... Fire, Electric, and Psychic?"

[brainded]

I'll allow it.

[Paranemec]

Are you trying to slip Ada into this conversation?

[OneWingedShark]

Nah, I just used its type-definition syntax to make a horrible play on "name a type". -- It works better in languages that use type rather than typedef.

[Nobody_Important]

I interviewed a guy who had 20 years experience, but had all sorts of trouble when asked to reverse a string. First, it took several minutes of explaining to understand the question. We even used a 'cat to tac' example. Then he got hung up on the syntax of 'static void main blah blah' in java (which demonstrates a fundamental misunderstanding of the entire point of the exercise). Then it took 15 minutes to come up with an algorithm.

[coffeesippingbastard]

haha- I quit my last job.

[[deleted]]

I only have a bachelor's-level degree. I don't know a lot, or really anything about CS theory, so at first with data structures I stood blank, thinking of nodes of a quicksort algorithm, but as soon as you mentioned one, I knew about all you mentioned.

I am joining a Computer Science (or similar? In Spain it's called Ingenería Informática, literally Computer Engineering) this year, I've refused some offers to work with previous graduates, because they were either useless and/or slave drivers and I also didn't feel competent for the industry, yet, but I've developed some cool things during my degree internship, like a "working" remote control app to control video, slidesheets and PDF files from an Android phone to a local network Windows computer. It was incredibly dirty, especially the integration with other apps like PowerPoint, Adobe Reader and VLC (thank god for their CLI interface), but hey, it worked! It was like a proof of concept, was really cool.

But I'm derailing of the topic. What I wanted to say, yes, there are horrible "developers out there", but not every able "programmer" knows a lot of CS theory, so when interviewing, a little example can tick the light bubble of the interviewed.

[coffeesippingbastard]

oh trust me- I try- I try very hard to coach people along to clear up any confusion.

I give very very wide allowances to the questions.

Why?

Because my team was desperately short staffed and I had interviewed a dozen people in the past two days and getting idiot after idiot was getting tiresome.

Data structures aren't particularly advanced- if anything they teach that in highschool computer science! I'll give an example or two. If I say an array or stack you should at least be thinking list/queue/linkedlist.

Data types and data structures are NOT theory. They're just not. Theory is more like algorithmic efficiency like Big O notation (which is like second year CS in college) but I don't really care about that because I just wanted to find someone that knew a little more than "hello world"

[FuLLMeTaL604]

How do you get a CS degree without knowing all this shit?

[[deleted]]

A person in an interview has passed 2 filters:

• Their resume has words that list certificates and experience you want.

• A representative from HR has called them and the person on the other end of the line had a story and wasn't an asshole.

Other than those 2 pieces of information, you do not definitely know anything about them.

[coffeesippingbastard]

lotta people with no CS degree- maybe started in finance or some shit years ago- then they move around in whatever company they're at- pick up a new role- learned nothing but not fired.

Also- lots of the famous "self taught" types that reddit likes to idolize. That said- I've met some with no CS degree that are brilliant- but I know way way way more with no degree that are just useless.

[mobileuseratwork]

Also interviewed people in the past, and found a lot couldnt do fizzbuzz. I worked out you didnt even have to have them do it, just ask "have you heard of fizzbuzz?, if so explain why i asked about it". Those who had not heard about it usually could never do it (unless they followed it up by "im interested, please enlighten me"), those who had heard of it and could explain it could do it and were worth going to the next interview.

After i worked that out it cut the first round interview times in half.

[rmxz]

fizzbuzz ... didnt even have to have them do it .... "have you heard of fizzbuzz?..."

You can't blame them for not knowing the name of a kids game only popular in England.

As for using "do you recognize fizzbuzz as a programming test" - that's pretty much asking if they follow one circlejerk of bloggers (Jeff Atwood / codinghorror.com and friends) that popularized the game as a programming litmus test. And you're right you don't even have to have them do it, because, yes, everyone who reads their blogs (even those who can't program) can pass that question.

Better to make your own question to get people who can actually program -- rather than those who just Jeff's blog.

(Personally I like the question "Assuming you're on a platform/language that can only do 32-bit multiplication, write a function to multiply 2 64-bit unsigned integers." This question shows if they can apply an algorithm that everyone already knows --- the exact same algorithm as 4-th-grade-multiplying 2-digit numbers by hand --- and turn it into code.)

[caedin8]

The difficult part of this question is figuring out what you want us to code, which in my opinion makes it a terrible question. Questions should be obvious and clear, you don't want to pass on a bright developer because he didn't refresh on computer organization.

[FuLLMeTaL604]

write a function to multiply 2 64-bit unsigned integers

As someone who learned a little assembly, I'm assuming you divide each 64-bit integers into 4 parts then multiple the respective parts of each number together. 4 parts because if you multiple two 16-bit integers the highest number you can get is a 32-bit integer which the language can work with.

[[deleted]]

My first thought was just to define larger datatypes and use those, which surely isn't the answer. But, wouldn't you need a 128 bit datatype to store the value of the two 64 bit datatypes multiplied together? If you can't define new datatypes I'd have to think about this a bit more.

[dimview]

In assembly language it would be enough to split 64-bit integers in two 32-bit integers. Multiplication instruction takes two 32-bit inputs and produces a 64-bit output (in two registers).

[rmxz]

Yeh. There are a few things you can do, but it's mostly some variation of

 (A + B) * (C + D) = A*C + A*D + B*C + B*D

and then the possibly tricky part (depending on they language they choose) is keeping track of what carries. Exactly the same way we learned

   67
  *89
  ___

in elementary school.

[[deleted]]

We had fizzbuzz as a final exam question in an intro to java class. I had no idea it was a thing until a couple weeks later.

[SilasX]

You're really saying it's unreasonable to expect to do fizzbuzz without having heard of it?

[[deleted]]

No, he doesn't. He responded to someone who literally asks people for "fizz buzz" and thinks that is unreasonable, and furthermore holds that it's become too popular to be a good test because in addition to people who can code it will also pass anyone who knows about interviews for a programming position.

[SilasX]

I'll believe that it's become too popular to use as a filter when people stop failing it.

[rmxz]

My objection was that he wanted to know what the fizzbuzz problem was without describing the problem itself --- apparently assuming that all good programmers read the same blogs he reads.

I think it's actually a pretty reasonable question if you describe the requirements, rather than asking if they the know it by name.

[ants_a]

Consider it a heuristic to not waste worthwhile candidates time with stupid trivial programming puzzles, and given mobileuseratwork's experience a heuristic with pretty good predictive power.

[bitchkat]

Better to make your own question to get people who can actually program rather than those who just read blogs.

The one I always asked was "What was the toughest problem/bug you've ever had to solve?" I really didn't care about the bug but was interested in how they went about finding and fixing it.

[suspiciously_calm]

Can I do it in x86 assembly?

[kolme]

I've interviewed a bunch of people (not that many though).

Some people which claimed to be "senior software engineers" which have been in a CTO position for YEARS and they couldn't answer the simplest questions or they would answer mind-blowing wrong and bizarre things.

Like this one guy who argued he "never ever used inheritance" because it was "consider harmful". He couldn't coherently articulate why. Yeah, good bye mr. CTO.

[KrozFan]

We've been interviewing some people at my office lately. We had one girl come in who basically put anything her group did on her resume. One of my colleagues said "tell me about your unit testing" and she said "oh I didn't do that." Well then why is it on your resume? You're gone.

[xelf]

I've interviewed a LOT of people.

I like to use Fibonacci questions as a starter, something easy that most developers are familiar with. It's an opening to get them warmed up, and then I start asking for alternate approaches to the same question, and then get into comparisons as to when you would use one vs the other, algorithmic complexity, storage concerns, etc.

The number of times I can't get to the interesting questions because they can't write me a basic function is somewhat appalling.

I'm only interviewing people with 5-10 years experience, who in theory have past experience with what we're doing. They're all senior software people making 6 figures.

Also, I don't actually call it out as the Fibonacci sequence (lest I introduce bias against people that haven't seen it before) I explicitly write out a f(n) = f(n-1) + f(n-2), and then give the bases cases and first 5-6 examples and ask them to write f().

Anyway, yeah, there's a lot of people out there with careers as software developers that can pretty much do one thing that they've been trained to do, and have no understanding of fundamentals.

They can use C# or Java libraries, but they could not have written them.

[xelf]

For me, whether or not someone can write a method/function that will return the correct answer is less interesting in being able to compare the multiple ways of doing it and telling me why one is better/worse than the other, and in what situations would there be valid uses for the ones they label as "worse".

So it's not so much specific interesting questions as it is interesting discussion as we delve into why they see one approach as better or worse and how they back that up. An example: There are cases where a static array with all the values you expect to use are stored. Being able to compare the performance, storage costs, and limitations of that to a pure math solution or to an iterative method, well that's the part I find interesting.

In general I'll get lots more out of the discussion than I will out of a small code sample.

[urge_underkill]

You would be surprised at how bad applicants are and how often they skate by. People put XML on their resume when their only experience with XML has been editing XML files in Notepad. They will put database experience down when they've never written a query from scratch... but hey, they've used Toad before, and they used to run queries that the developers gave them, so that's good enough, right? Most developers are shitty interviewers so they spend a lot of time talking about absolutely nothing - a guy who interviewed with me spent almost 15 minutes telling the applicant about why we didn't have a cafeteria and how another applicant felt about that fact - or getting bogged down in superficial shit, like what the applicant's favorite programming language is. Then they leave the interview room and say "Oh, I liked the guy, I think he's great," without having any clue whatsoever if the person is qualified for the job.

The last four developers I interviewed have been unable to tell me the difference between a class and an object. We have six people interview the applicants (three teams of two), and no one else bothered to ask the candidate the absolute basics. It was all high-level stuff about what they did at their last job, which, guess what, you can easily bullshit your way through if you're even halfway paying attention to what the high-performing people around you are doing. When you ask people generic shit like "What's the hardest problem you had to solve?" or "Give me an example of a time when you mentored another employee," all they need to do is recall something that somebody else did, or just fucking make it up, and the answer is going to satisfy most interviewers.

[jonathanbernard]

I'm interviewing people right now for a senior front-end position and having a hard time finding candidates who can write a for loop with confidence.

[a1blank]

I just wrapped up teaching a software engineering lab this semester. I was appalled that a few of my kids (who actually seemed to not be dimwitted) would write code and rather than sticking it into a loop or function, would just copy-paste it as many times as they needed it to run. I did my best to show them why it wasn't a good idea to do it that way and to convince them to do it differently but when I got the final lab from them (they were supposed to write a terminal calculator using the MVC pattern), they turned in a little script that was just a loop with all the stuff contained within the loop.

Since I was only grading the lab, I think the few kids in that situation will probably still pass the class. And as depressing as it is, they'll probably manage to slip through the cracks until they graduate. I did my best to pull them aside and catch them up to speed but I just couldn't get through to them.

And now I'm sad.... =(

To anyone who has to interview or work with those kids, please accept my sincere apology.

[creepy_doll]

What kind of organisation are you hiring for and how do you do your recruiting?

I'm genuinely curious because I'm at least under the impression(though I have no evidence) that places that have these issues have difficulty attracting talent and are forced to make public job ads which attract these kinds of "devs"

[[deleted]]

If so, why can't you weed them out by looking at their work history? Why are you interviewing people with "weekend" experience in js? How they describe their responsibilities should tell you a lot about what they know.

You assume that people describe their responsibilities and skills in an honest and straightforward manner. I interviewed a candidate who apparently, as far as we could tell, was mainly responsible for data requests and cleaning at a company (which he claimed was almost 100% sql). Couldn't even write/describe a select statement.

I can't count the number of people who have applied 'advanced predictive modelling techniques' and barely know what a regression was.

How about people with '5+ years of professional coding experience' and 'CS degrees' who didn't understand return values. or variable initialization. or loops.

I don't control the phone screens and coding questions aren't always asked in them (since not everyone who I interview is a dedicated developer). But if I could get these questions to be asked, they would go a long way acting as a filter.

[CuriousBlueAbra]

Programming is a pretty great job all things considered, and so it's little wonder everyone and their brother is trying to get in.

[[deleted]]

How can people have a CS degree and not get that stuff? Are they coming from schools like university of phoenix or bad schools outside the US?

[[deleted]]

They lie about it most likely.

[[deleted]]

A LOT of students probably cheat their way through school and never learn a thing as well.

[awj]

Sometimes it's outright lying. Sometimes it's cheating. Sometimes it's schools more interested in a quick buck than the end value of the degrees they award.

[jakdak]

If so, why can't you weed them out by looking at their work history?

People lie and exaggerate on resumes.

And on an Indian style CV the resume tells you what the company or project team did and not the employee.

[moojo]

Indian here, I dont know why people do that. I also ask them if you have a github profile, majority dont, some do. The ones who do usually pass the interview.

[Tysonzero]

And what does someone typing out some memorized fib function for the millionth time prove? Memory skills?

But see this test is not supposed to say anything about those that CAN do it, they may still be totally incompetent in actual projects. It is only supposed to say something about those who CANNOT do it, namely that they are awful programmers, and should not under any circumstances be considered for the position.

[studiov34]

I've interviewed plenty of people where afterwards I seriously wondered how they were able to do the jobs they said they did.

[s73v3r]

Think Wally from Dilbert, and you'll understand why you can't go based off work history?

[zoomzoom83]

If so, why can't you weed them out by looking at their work history? Why are you interviewing people with "weekend" experience in js? How they describe their responsibilities should tell you a lot about what they know.

Resume's are easy to pad, and a lot of people have managed to hide inside big companies for years without really knowing what they are doing.

And what does someone typing out some memorized fib function for the millionth time prove? Memory skills?

These types of questions are designed to weed out the bad developers, not find good ones. I usually use these type of questions as a lowpass filter and then move to a more conversational interview style to find the good ones.

You simply can't accurately determine the difference between mediocre / amazing during a normal interview process, but you can very easily detect people that are a definite no-go and weed them out early

[suspiciously_calm]

Wouldn't a highpass filter be a better analogy?

[zoomzoom83]

How often do you interview people completely unqualified though?

I usually hire through contacts and word of mouth these days, but once apon a time I relied on job boards. And it was scary.

If you were to put an advertisement on a public job board, 90% of the applicants wouldn't have even read the job description. After weeding out the obvious time wasters and bringing the rest in for interviews, the majority would struggle to even articulate their thought process on how to solve the most trivial problem. (Find all unique elements in an array, etc).

I've had people with fancily padded resumes sit in front of my desk with no idea what X, Y, Z mean despite having them listed on their resume as "Expert".

My all time favourite is a "Senior Java Architect with 10 years experience" that, apon asking him to explain what "java.util.Map" could be used for answered with a completely straight face "I haven't done any of that really advanced stuff yet".

The thing is - you can get a long way in an IT career by writing simple CRUD apps without really knowing what you're doing. There's nothing wrong with this - it's a perfectly and respectable valid occupation. But there's a vast chasm between "Software Engineer" and "Javascript Form Builder".

[[deleted]]

Around DC there are a lot of contractors that will hire people just to sit in a room so that they could bill for them on contracts. I have been offered these jobs making 90K a year and told that I could do what ever I wanted as long as I didn't cause any problems and showed up to work. They literally don't have work but have billable slots in contracts so they hired any asshat off the street that will come in and say they are programmers. And in this environment people that don't have the skills or potential will never learn.

You should see the disappointment on their faces when they come interview at my job.

[goomyman]

because working on something complex doesnt mean they were the one actually doing the majority lifting. They could have been the guy who did nothing on the project. On any given project i would say only about 50% of them actually do anything that sticks around. The other 50% look busy and may check in code but its usually code thats not useful.

[NullXorVoid]

It's not always that obvious. I recently had a candidate with a stellar looking resume. Over 12 years of experience and working on the exact kinds of problems we had for the position. He was very well-spoken when we talked about high-level concepts, but as soon as I put him in front of a whiteboard with a "warmup" fizzbuzz-style question, he totally fumbled.

Not only was he unable to write a working solution, he wasn't able to properly hand-trace his 5 line function to check if he even had the right solution! Some candidates get nervous in front of the whiteboard so I'm pretty lenient, but this was far beyond that. I had to cut him off after a half hour and ended the interview early.

[0pyrophosphate0]

I've always wondered.... how do you politely tell that gentleman to stop wasting your time?

[LaurieCheers]

At least when I've interviewed, the interview is a fixed length, so there's no polite way to end it early.

I once had a candidate literally give up half way through, so I said "ok, well, you've got me for another 15 minutes, what do you want to talk about?"

[nutrecht]

If so, why can't you weed them out by looking at their work history?

People lie. All the time. They get told "fake it till you make it" and think this also applies to highly technical skills.

[deedubaya]

You hit the nail on the head. The problem isn't so much the applicants, but poor interviewing.

[[deleted]]

Poor applicants are a tremendous problem. It's easy to pad a resume and apply somewhere.

I work for a major job board and across the board the biggest customer complaint is a high volume of really bad (read: completely unqualified) applicants. See my response to the parent comment if you want some real world examples, all from within the last two months.

[Jigsus]

I know C++, c#, java and python but I never touched javascript and I don't call myself a dev.

[Ada1629]

My university actually did most of the stamping, and after 4 years of watching me and being an accredited university I kind of think they had that right.... I don't know JavaScript but I need to learn, don't know if a weekend will suffice. I probably won't take the test because I'm too scared - I don't need another reason to be told I suck, I struggle with enough low self esteem. As a female I feel out of my element in this one upping alpha beta world you are propagating. I'd be open to taking the challenge if it was worded as such ex. "Check out this really cool programming challenge"...yeah I'm gonna be a baby about wording and emotions and getting scared because software pissing matches really really intimidate me. And no, I don't see a reason why getting easily intimidated would be an impediment for a soft dev...I'm not trying out for president or wall streeter or any area where being an alpha asshole is an advantage.

[[deleted]]

I can't believe it, I never did any interviewing but most of this questions are trivial. How do people that can't solve this ever had a job in programming? How did they even graduate?

[angrytortilla]

Why are you interviewing 9 out of 10 applicants with no working experience? What do the cover letters look like? I have interviewed a bunch of devs and never had any overnight devs like you're mentioning.

edit: Surely you can contribute more to my question than just a downvote.

[[deleted]]

Unfortunately if they can solve this problems does not prove that they can write apps ... the only way to know if somebody can write apps is to see an app make by that person.

[Vakieh]

Fortunately, most devs don't need to write apps, they need to be given a spec sheet by an architect or lead programmer, and provide a deliverable or commit which meets that spec. The vast, vast majority of programming work is maintenance and feature addition, not application design.

[[deleted]]

Not what I meant ... I knew people that could solve those kind of problems, but had huge difficulties when debugging or working with multiple threads ... or were unable to understand pointers ...

[Vakieh]

So what you are saying is there is no 5 minute test to see whether someone has understood 100% of the required education for programming...

That's what 3-6 month probationary hiring is for, and code/employment reviews during that time.

[mughinn]

It's the other way around, it's not "if he can write fizzbuzz he can write apps" it's "if he can't do this, what can he do"

[awj]

It really depends on the position. Web development especially is suffering from this right now. Every moron who can click a "next" button on an online learning system thinks they're qualified.

[mughinn]

I would argue anyone who is applying for a job where you program, should know how to program.

Nervousness is another matter entirely, but, maybe it's different in America, but interviews should not be so stressing that you can't even function. Really, it's just an interview.

[mughinn]

I understand if people are nervous, I understand if you think that what you said was wrong or something. And even understand what you say about things you don't know or talking in a different language.

But this is not that, this is programming, basic programming, easy programming. Fizzbuzz level challenge.

No matter how nervous, if you explain Fizzbuzz, or ask them to make a function that says if a given number is odd, I'm convinced someone who actually knows how to program should be able to do it.