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Ask HN: What % of your job interviewees pass FizzBuzz type questions?

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Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#81

Post by pp13 »

eropple wrote: post #72
pp13 wrote: post #70

Earlier quoted context omitted.

@eropple So do you have data to back up your claims that; answering those questions determine if your a good programmer. Yes, there are tons of programming jobs out there, that don't require much of those skills. Not all jobs are that innovative. Most of the development jobs I have seen require you to come up to speed with the code base fast. So it's that code reading comprehension that I think is most prevalent.

I did not in any way, shape, or form claim that such questions determine whether or not a candidate is a good programmer. If you are going to respond to my posts, please respond to my posts and not what you think or wish I said in those posts. No interview or interview question can determine conclusively that you are a good programmer. But they reduce the likelihood that you're not, and comments like your strident an…

Ok, I didn't mean to offend you, I am sorry if I have.

That being said these are my thoughts on the subject of interviewing programmers.

When I just graduated college, I was all about puzzles and programming puzzles. My thoughts were that only people who could do these puzzles deserved programming jobs.

I was so wrong. Puzzles are something that you get or don't get. If your in an interview, and you haven't faced those combinatorial problems for a while, you could bomb, if someone asked you those questions.

Understood "fizzbuzz" problems are suppose to be the the lowest level of programming problems that any competent programmer can solve. If you want to fast screen candidates, go ahead and ask them.

When you get into problems, that require "tricks", either you get it or don't. It could be easy for some people and hard for others. There is no correlation of them getting it, to being good on the job, unless the problems are such that, the programmer will face them every day on the job.

Another good permutation problem, is subset sum problem. Come up with a program that determines if a array or list, can be partitioned into 2 non overlapping subsets, such that the the sum of both subsets equals each other. Print out both subsets if they are equal or state that it cannot be done. Is it possible to get better than O(n^2) for the optimal solution. That is fun one, but I don't think asking that would give you much insight into determining whether the programmer is fit or not.

I think interviewing is a really important task. It a really hard job to get right. If your a bad interviewer, the company you work for will eventually get a bad reputation.

Many software companies do not train people how to interview. That in our industry, is a huge problem.

There are many other things besides raw technical skills that will determine, how well the candidate will do at their job and at at the company.

Going over the candidate's experience in detail. Getting a feel for what they really want and expect from the job. Do you like the candidate's personality? What does your gut instinct say. What technical things do you need to ask that are relevant for that job, that you couldn't determine from the their experience? How would you design questions, relevant to the job at hand.

Just my random thoughts.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#82

Post by sigjuice »

dlikhten wrote: post #47
hga wrote: post #29

Earlier quoted context omitted.

Back in the days when I did this (1990s) we did the C/C++ reverse a linked list and compute the factorial of a number. And, yeah, people made mistakes on a dry erase board under interview pressure, but it was very clear who has a clue vs. who couldn't program their way out of a wet paper bag. These sorts of tests are low pass filters, they're not designed to find good or great programmers, just confirm that the perso…

Give em a laptop. Those are a dime a dozen (we got a ton sitting around the office). Have em code in front of you. Hell I'd install any interpreter within reason to let em solve it.

Amen. Who writes code on paper in real life anyway? The font is wrong, there is no backspace and you can't insert and remove lines. Interviewers have some nerve demanding proper syntax.

Give me a laptop with just a text editor and watch over my shoulder.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#83

Post by ig1 »

pp13 wrote: post #49
aplusbi wrote: post #31

I've never asked FizzBuzz but I do regularly ask coding/algorithm questions. They are usually more difficult than FizzBuzz. I'd say around 80-90% can at least come up with a solution in 45 minutes with some help. Probably less than 10% can come up with a good solution entirely on their own. I attribute this to two things, first I think our phone screenings work well enough to keep out people who really can't do FizzB…

@aplusbi Let's say I interviewed you. I had asked to implement the fastest algorithm to give back the largest palindrome of words in English dictionary and compare it the largest palindrome of the french language. What the best solution you can come up with in 45 minutes. After, that I asked you, write a simple ftp server, in the language of your choice. With your first solution, I asked you implement a SSL library a…

The problem with that is that there are plenty of programmers who can talk the talk without being good programmers.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#84

Post by ig1 »

aplusbi wrote: post #37
spamizbad wrote: post #27

4 candidates, 2 passed FizzBuzz. Oddly, the two that failed had a Masters in CS (albeit no BS in CS). Of those that passed: one had Masters in Library Science looking to change careers. The other was a fresh out of college CS major from Illinois State. Next batch, I think we'll add another trivial question: count the number of vowels (a, e, i, o, u) in a string.

I've been involved in a lot of interviewing/recruiting especially of recent graduates. I don't have hard numbers, but it seems to me that the candidates who have masters degrees tend to do worse.

It wouldn't surprise me, I suspect a fair amount of Masters students are studying for a Masters not because they want to further their education, but rather because they want to avoid going into the real world because they know they're not good at programming.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#85

Post by lotharbot »

wladh wrote: post #68
dlikhten wrote: post #47

Earlier quoted context omitted.

Give em a laptop. Those are a dime a dozen (we got a ton sitting around the office). Have em code in front of you. Hell I'd install any interpreter within reason to let em solve it.

It's not about how expensive a laptop is or isn't. If somebody can't master the basic syntax of the language so that they can write a very basic algorithm without syntax errors and in such a way that it would run on the first try, they can't be very productive. And fizzbuzz is really the rock-bottom of the simple algorithms. Even a linked-list library would be a very reasonable thing to ask (if we're talking about C…

Writing on a whiteboard while explaining yourself is different from typing alone into an IDE. Conventions you might use to avoid syntax errors (like typing a pair of braces and then filling the middle) may not work on a whiteboard. Pacing is different, and muscle memory doesn't help. You're looking at a blank whiteboard rather than your terminal with other parts of the codebase. The first few minutes of coding are often "getting up to speed"; many programmers are orders of magnitude more productive once they're "in the zone".

In short, I wouldn't consider "your whiteboard code is missing a semicolon" to indicate a lack of productivity overall, only a lack of practice coding on a whiteboard. (It surprised me how much better my whiteboard code got over the course of a quarter of teaching.)

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#86

Post by jimminy »

mikereedell wrote: post #34

While we don't ask FizzBuzz in particular we have a question my manager asks: If you could fold a piece of paper 50 times, how tall would it be (very rough ballpark figure)? Our success rate is surprisingly low.

On the assumption that your question is verbatim what you give applicants, I'd say your success rate would be low. Your question lacks appropriate definition to be solved, in it's current state.

You have multiple types of folds that could be made, variable on direction, orientation, and fold distance. The only one really pertinent to this problem is fold distance. A paper folded 50 times could be 51 * thickness, if you don't define that the paper must be folded in half each time. If you enforce that it must be folded in half it becomes: (2^folds) * thickness.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#87

Post by aplusbi »

pp13 wrote: post #49
aplusbi wrote: post #31

I've never asked FizzBuzz but I do regularly ask coding/algorithm questions. They are usually more difficult than FizzBuzz. I'd say around 80-90% can at least come up with a solution in 45 minutes with some help. Probably less than 10% can come up with a good solution entirely on their own. I attribute this to two things, first I think our phone screenings work well enough to keep out people who really can't do FizzB…

@aplusbi Let's say I interviewed you. I had asked to implement the fastest algorithm to give back the largest palindrome of words in English dictionary and compare it the largest palindrome of the french language. What the best solution you can come up with in 45 minutes. After, that I asked you, write a simple ftp server, in the language of your choice. With your first solution, I asked you implement a SSL library a…

Like I said, 80-90% of candidates can answer my questions. I am also very generous with what I accept as an answer and how much help I give. My interview is as much a discussion about the question as it is the solution.

As for what I get out of the interview - you're right, it's not going to tell me how good of a programmer the candidate is. But it will tell if they can code, and will give me some idea of their problem solving abilities. (I've also personally solved both questions without help in under 15 minutes each, though not under stressful interview conditions).

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#88

Post by aplusbi »

unshift wrote: post #75
pp13 wrote: post #49

Earlier quoted context omitted.

@aplusbi Let's say I interviewed you. I had asked to implement the fastest algorithm to give back the largest palindrome of words in English dictionary and compare it the largest palindrome of the french language. What the best solution you can come up with in 45 minutes. After, that I asked you, write a simple ftp server, in the language of your choice. With your first solution, I asked you implement a SSL library a…

couldn't agree more. if i had to come up with a permutation algorithm as part of writing code, you'd better believe i'd look one up so that i'm sure i'm doing things optimally. i wouldn't trust myself to come up with the exactly right algorithm on the first try. if i had to deal with some weird half-sorted array, i assume i'd be working in the same context as the problem and wouldn't have to make up a solution on the…

These questions aren't about "real world" situations, they are about problem solving and basic coding. Questions are good, as is a discussion on how and why these things should be implemented.

For the split array problem I rarely ask for code (only when I think it will actually help the candidate), it's just a discussion. It usually goes something like this:

    Candidate: Well I can sort it first, then do a binary search.
    Me: How would you sort it?
    C: I'd use quicksort.
    M: Can you do better than an nlogn algorithm?
    C: Well I suppose since it's two pieces that are both already sorted, I can just find where they are split and then rearrange them.
    M: How would you find the split?
    C: I can go through each number until they stop increasing.
And so forth. The "best" solution (that I've come up with, anyway) is to find the split using a modified binary search, and then use a regular binary search on the piece that might contain your query. Not everyone gets that and that's okay.

In addition to asking coding questions I always ask candidates about previous experience and projects they've worked on. Sometimes the answers to these questions are more important. Most of the people I have been interviewing, however, are recent graduates or students who are just finishing college and may not have much experience or many projects that really engaged them.

I spend a lot of time thinking about how I can improve interviews within the confines of how my company conducts them. I've stopped asking the permutations question as I feel that it has too much of the "aha!" factor in that either the programmer goes "aha!" and solves it or they don't.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#89

Post by kaybe »

hga wrote: post #35
kaybe wrote: post #23

Earlier quoted context omitted.

How would I go about programming my way out of a paper bag? It creates the weirdest ideas and images in my mind.

Oops, although this won't help your mind ^_^, the correct expression is "... out of a wet paper bag". From more apropos usage about fighting or escaping from such a flimsy thing. And now that you mention it, I have no idea either ^_^ ... except that it ought to be easy. In that last company where I was part of the hiring process I myself got the job only because I was the only one they interviewed who could pass thei…

Maybe if there was a robot to program, I guess that would count.. now that would be a great opening move on part of the company! :D Let's see.. you'd have to get the robot into the right position (maybe find it with sensors - what kind of wet paper bag are we talking about, the dark kind?) and control another part that's capable of ripping the bag. Depending on the size of the robot you'll have to move it around a lot to make a hole big enough for yourself. Of course, you can also have the applicant design a robot for that task.. uhm, I'll stop now.

Re: Ask HN: What % of your job interviewees pass FizzBuzz type questions?

#90

Post by iron_ball »

elliottcarlson wrote: post #33

I have used various interview questions, including FizzBuzz, factorials and other questions, and I would say the success rate I saw was about 20%. My personal favorite question is to have someone write a shuffle function without using any built in randomization functions - however most people give up, and others can't follow simple directions and wrap their head around the problem. This particular question had more o…

Do you meant that they can't use Array.shuffle() or Array.sort()? Or that they don't get any external source of randomness, even a 0.0 - 1.0 float?
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