Microsoft changed how it interviews software developers
businessinsider.fr
businessinsider.fr
One of the key issues in recruiting is how to make hiring decisions quickly. Good candidates don't have the patience for your internal politics to resolve over a month or two to figure out whether they're getting an offer or not; they're just going to interview with other places in the meantime who will beat you to the punch.
Take a resume off the pile. Email or text to schedule a call. During the call, talk about relevant experience / past projects, what each side is looking for, etc. Make a decision during the call whether you want to invite the person for a two-hour interview, and schedule it during the call, first offering an evening time slot for the interview. In the first hour, talk about culture, problem-solving and teamwork approaches, engineering attitudes. In the second hour, pull out an actual current problem and solve it collaboratively. If all goes well, send an offer, and offer to set up a dinner to talk about / negotiate the offer.
It should not take more than a few hours to make a decision on someone; it should not require a candidate to take paid time off. Your hiring pipeline's average lead time should be measured in days.
It seems to me this is an issue with your employer not the interview process.
there is only so many days i can take off. with two weeks holidays, i might spend all of my holiday budget for this year.
by stating that it is most certainly not just once as i am likely interviewing for multiple jobs.
i don't know what the solution is, but i think it is reasonable to say that some compromise is necessary, and as much as i value your (and my) time with family, if we want to grow our team so that we are not having to work overtime as much and actually get more time for our families, then we'll just have to make some sacrifices.
apologies for being a bit polemic.
actually, i do have a solution for myself. i only hire young people fresh out of university who don't have a job yet. higher positions are filled from within. ask me in a few years how well that's going.
I'm honestly not sure it is. Half-a-day to a day of on-site interviews (possibly after a phone screen) is how most companies have been filling professional roles for decades. Certainly it's an easier process for people doing it out of university. And it's easier to do locally when a candidate can often just take a few hours off. But, while many debate some of the specifics of how companies screen for technical talent, I don't see widespread pushback against candidates coming in for on-site interviews of some sort.
Why are software engineers doing interviews at all? What makes software engineers qualified to interview people (especially when you consider the need to avoid hiring bias, problematic statements by interviewers that expose the company to legal suit, etc.)?
I'm not saying that companies should go to the other extreme and have all interviews conducted by HR - that presents its own set of problems in that HR doesn't know how to evaluate candidates for technical skill. But expecting hiring managers to open up a few evenings per week in the irregular and relatively uncommon circumstance (if it's common, then you have problems with churn on that team, and you should consider firing the manager) in which positions open up on their team to evaluate potential direct reports is not even remotely unreasonable.
i do want the opinions of the people already on my team, because a big part of the interview process is to find out how well they work together. for me hiring is a team decision, not a top down mandate. so yes, all of my software engineers will be doing interviews. there is no way around it.
on the other hand i agree with you. these rounds of interviews should not happen to often. if our team grows, i expect to add two more positions every quarter. (i don't know how realistic this is, but this just to give you an idea of how much interviewing workload i expect.)
That being said, if a candidate just couldn't take off work for whatever reason, I am willing to do an evening interview.
Gotta be flexible, on both sides.
I'm currently interviewing and so far I have had a 48 hour weekend project, a 3 hour code assessment, and I'm expected to endure 3 days of interviews. I'm fairly close to throwing in the towel and saying I can't be arsed with this.
You had a lucky escape. I had the same from a company. Which was arguably a 2 full nights worth work if done right.
I took the challenge. Did it, it passed their functional test suite which they provided. Unit test cases, git repo, documentation etc etc all in place.
They came back saying it was not enough. So it's not like if you do the take home project, they let you in.
Also its a tad little irritating to make people work for so long, make them do everything. And even then with perfectly working solution turn them down.
Further inquires about what was wrong, given that it was working as per specification got zero answers.
Anyway, this all seemed perfectly reasonable until I went for a job I'd been approached about by an agency with a similar test at the beginning of the application process. They'd asked me to build a simple calculator and said it should take no more than 2 hours.
No big deal, but it was the weekend before I had 2 hours free where I could do it due to other commitments. Pushy recruiter didn't understand this but, whatever[1]. Should have been a red flag straight away.
Anyway, I put together a working solution with comprehensive tests, send it off to the recruiter and on Monday hear... nothing. That's right: nothing. Gave it a few days, got in touch with the recruiter and still nothing. No, "sorry, it wasn't good enough." No feedback on what might have been wrong with it. Nothing.
I was absolutely incensed. The whole incident gave me a different perspective on pre-interview tests, to the point where I'm no longer really interested in doing them for "unknown" companies. I made an exception to work with an organisation where I had several friends, so was confident that even if I didn't pass I'd get some decent feedback on why.
The most significant effect, however, has been on my own approach to recruitment. At the moment we don't, and I have no plans to introduce, programming homework as a pre-screener. Rather we take a much more personalised approach. We're also in the situation where we get few enough applicants that we can afford to talk to all of them, although this won't scale and will have to change.
Still, it's hopefully uncontroversial that before you invest the 5-6 hours (across 2 people) required for a 2 hour technical interview (in our case an exercise where we work together on a problem), you do need to some sort of pre-screener to weed out the people who really can't code: https://blog.codinghorror.com/why-cant-programmers-program/. I wouldn't say this is 99 out of 100 programmers, nor anything like, but it's certainly the majority. We therefore do a half hour telescreen, which is a fairly informal chat about what the candidate has been working on, what we do, and then - of course - there's a very simple programming task at the end. This takes an investment of roughly 90 minutes on our side (again, 2 people). We're explain the format to candidates in the invitation, which gives them an opportunity to decide whether they want to go through with it or not.
Even if candidates don't pass, and it's usually on the technical task that they fall down, we give them feedback, including pointers to how they can improve their skill level.
(Apologies, this came out much longer than I intended.)
[1] There's some merit to the "well, do you want a new job or not?" mode of thought but not much. E.g., in my current role I advise candidates not to do our technical interview after a full day of work because they're not likely to perform at their best. Obviously not always possible, but it's about ensuring they set themselves up for success: if you dislike your current job enough to be looking for another one don't you want to make sure that when you get an interview you do everything you can to do well in that interview? This is obviously very different to expecting candidates to jump through hoops under time pressure just because "commitment".
What I've learned is that it is a very weak signal to talk to candidate about "their research" unless it's immediately and directly applicable to what we were doing as a company, so that we can talk about it as equal experts, which never really happened in our case. Previous research done by candidate was, like research almost always is in a narrow and specialize niche. Every candidate I was talking to was very good with talking about their research and from my perspective at the time of the interview it was impossible to validate and evaluate their claims. That conversation could convey the character of the candidate but I couldn't evaluate their ability to do new research.
Instead, presenting candidates with the same problem, that in our case took around 3 hours to solve, in our case proved a good way to compare candidates a bit more objectively and test how they approach solving problems they haven't seen before which is more applicable to what they'll be doing on the job.
The downside of that process is that during three hours you can only test so much, but hiring is a really hard thing to do right and we didn't want to take more of candidates time as we did value it highly and found that to be the sweet spot for us.
It all depends on the questions asked to the candidate. You don't ask them about their research which is publicly available in any case. You ask them questions that let them reveal their thought process about their research. Now, it's up to the interviewer to come up with good questions to make this happen. The interviewer has to be well prepared and think about questions. You don't need to be an expert to ask good questions.
I'd like to reiterate that this applies to research/scientific position where pushing the boundaries is a crucial aspect of the job. In case you are looking for a very specific skillset, things may be different.
What too many people choose to forget or ignore is employment itself (at least in CA) is a 2-way process. The employer is not doing you a favor by employing you, despite how many people have drank the kool-aid to the contrary. You and the company have entered into a mutually beneficial agreement. Unfortunately, many people don't have the means or desire to walk away when an employer veers into "you should be thankful we let you work here" territory.
Any serious interviews will take a day extra traveling, your prep time etc - I agree about having 4-6 interviews in a day is just stupid.
This may not apply to all companies or situations, but for a Microsoft-sized organization this is the way it should be done.
Your hiring needs should reflect the size of your organization, and your hiring process should reflect your hiring needs. If you hire relatively infrequently then it makes sense to go over individual resumes and have infrequent evening interviews. If you need to hire hundreds of people this month just to negate churn then you have the resources to build out the kind of enforcement-process-oriented above since you surely need that kind of infrastructure anyway. Everything in between is just a matter of degree and where your company is on the process-vs-culture balance as a function of its size.
However TBH an in-person day with 4 or so interviews (perhaps post a phone screen) is absolutely standard for all sorts of professional positions and has been for many decades. I can only think of one case where I just had an informal in-person lunch instead--and that was a case where I knew the company's owner very well.
This is me. Hard to get that across in an interview, but once people work with me, they're cool with me coming back an hour later in an email with some thoughts on the last meeting topic. They know and respect that that's the way I work[0].
[0] I'm not the only one on the team who does this, so that helps.
I have done plenty of architecting. A large percentage of architectural problems that you are asked to solve have already been solved. After enough years at enough different companies and reading enough architectural books, it’s just pattern matching and figuring out the correct tools.
https://www.amazon.com/Domain-Driven-Design-Tackling-Complex...
https://www.amazon.com/Clean-Code-Handbook-Software-Craftsma...
https://www.amazon.com/Clean-Architecture-Craftsmans-Softwar...
https://www.amazon.com/Patterns-Enterprise-Application-Archi...
https://www.amazon.com/Refactoring-Improving-Existing-Addiso...
https://www.amazon.com/Code-Complete-Practical-Handbook-Cons...
https://www.amazon.com/Pragmatic-Programmer-Journeyman-Maste...
https://www.amazon.com/Mythical-Man-Month-Software-Engineeri...
And just because it’s asked at every interview.
https://www.amazon.com/Design-Patterns-Object-Oriented-Addis...
I’m focused on AWS these days, but a lot of these principals are universal.
https://d1.awsstatic.com/whitepapers/architecture/AWS_Well-A...
It's meant to characterize people who think about what they should have said/answered only when on their way out, in the staircases.
I think I work this way. Maybe it's a way to ignore my lack of wit, my slow paced brain, and to maintain some self esteem.
Given that many people report that their best thinking is done while walking or taking a jog, it might not be too wild to try out interviews which allow the candidate to take a walk before they give an answer.
the problem i see is this:
it is unexpected, so the interviewee doesn't know what to make of that offer.
i don't know how much time to give them, and they don't know how much time they need. they also don't know how much time they should take.
i don't even know if they are the type that likes to take a quiet time to think. if they aren't then that offer could come across as a suggestion that their answer is wrong and they should think about it more.
at best it would be some institutionalized coffee-break, like we do the interview in two parts, first we are doing a bunch of exercises, then we take a break and after the break we do something else, but the interviewee is offered to add thoughts on the exercises that they may have come up with during the break.
Of course, you can also just leave the room while they're working on it.
I tried to find some way around it, and the only way I see is to learn how to think loudly. The only way is to supress others from thinking by speaking aloud my thoughts as they come. Let others follow my thoughts, not the other way around. I figured it out while making some group work with ~20 yo students being a student myself. I'm older (I was 35-40 over that period) and therefore smarter and in the most cases I was able to do this group work myself a way better then they do.
I tried different approaches. I tried to take a leader role in a discussion and to talk everytime I feel like this. I tried to let someone else to become a leader and to follow her. I tried to just get out of the discussion, to sit quietly with my own thoughts and to come with my own solution to compare it with the group one. The conclusion is: I cannot think AND listen at the same time.
It's probably not that these candidates can't think on their feet, it's just that they generally aren't willing to compromise so greatly on accuracy and quality of the answer.
just had that happen. we had an overloaded server, and while we tried to figure out how to make the server faster, after some thinking we realized that the better long term solution was to change some of the architecture so that the server would get less load to begin with.
that was definitely not what came to mind first.
I've worked with people that were reactive and would love to be "the fixer" when, in reality, 99% of the issues he fixed were caused by his ignorance/incompetence in the first place.
Specially for crucial 24/7 roles, you need people that think ahead and not reactive ones.
It is precisely because of my experience that my team is OK with me taking an hour to ponder.
Edit: Let me clarify one thing. I'm not talking about situations where, say, the PO comes and asks, "Hey, JustSomeNobody, why does the system do this under these conditions?" I know the answer to this. If they want logs for that specific instance, I can get them. What I'm talking about is, when the PO calls a meeting and says, "I just got off the phone with <Entity>, they want these changes to the system. What will it take?" I don't answer these questions, definitively, without thinking about them. That does NOBODY any good. I'll sometimes give a few initial thoughts for the sake of the meeting, but that's it.
they asked me to build something. I used dictionaries and wrote the code in ten minutes.
Both interviewers wouldn't believe that the code could solve the problem.
They later told me that dictionaries are not used in practical applications. Never understood why.
Are dicts not used in "real life"?
Plus they were giving me (x%) a raise, and I got (x-5)% in my current company. So thank God I didn't join there. Contacts are more important than salary.
When the topic is something where I know some underlying complexity exists, or the stakes are high, I often want to spend a bit of time thinking it through by myself because that's how I think best about those sorts of problems.
I've encountered friction at times with those that aren't familiar with and/or care about the underlying complexities and just want to talk high-level and make decisions and move on. Sometimes it is important to make quick decisions to avoid analysis paralysis, but often it is worth giving those who do best thinking through things on their own a chunk of time to go off and do what they do best. I wish more people took that into consideration when conducting brainstorms.
Fundamentally: Why are you having the "Can you code your way out of a wet paper bag" conversation instead of the "How much value can you add to this company" conversation?
Perhaps my experience as a consultant/freelancer is breaking my perspective. It's been several years since I last had a coding interview as an applicant.
Right.... so if you have a mismatched role, that's it, you're done for, huh? Please.
You don't want to "apply" for things. You want your google VP to be having a beer with your ex-boss and worrying that his pet project was going to fail because they just can't find a guy who can really $X.
But your ex boss knows a guy who absoulutely can $X, and just finished $X'ing his company back from the brink of disaster. Lets give him a call to see if he's available.
HR will be told to give that guy an offer and, optionally, collect a resume to keep on file.
That's what we're talking about here, and it's where you want to get yourself if you want to build a career as an individual contributor.
If they buy the company that you built specifically to get access to you, do you think you'll still end up getting screened out by some junior dev on a whiteboard? All policies have exceptions. Your goal is to be exceptional.
In this case probably not, but you'll have to do several rounds with the VPs. Of course the tenor is very different, more conversational / situtational instead of technical questions. But you're still being sniffed out. Unless you're already pals with the VP.
Edit: I see from your other post you haven’t interviewed since 1999. Sounds about right. The hiring process does not work how you think it should.
From talking with other devs in my peer group, this doesn't seem uncommon.
Could you elaborate on that? Do you mean being a contractor should be your goal as "the guy" or the hirer?
No, HR will be told to get that guy into the interview pipeline as soon as possible, so he can go through the same process everybody else does for a similar position.
Some people will be at the top of their field. Most people won't.
It can make sense for consultants, doing short gigs here and there. People can refer you elsewhere when the current work is completed, they ain't gonna keep you anyway.
Since then every gig has come via an introduction by a former boss or co-worker, or by introducing myself to somebody with hiring authority and using a pile of impressive artifacts to skip the "can this guy do the work" questions.
The first several years of your career should be getting yourself into a position where nobody would ever dare ask you to sort things on a whiteboard.
Because people lie. It's that simple. Referrals lie, CVs lie, friends lie to get friends in a position. Do understand that there's a fundamentally different set of problem a 40.000 FTE company has to deal with in comparison to a 30 person startup.
Also is doing a full day interview really such a horrible sacrifice for most paid jobs in the world? Professions like laywers and doctors need to go through significantly longer hazing rituals to get to FAANG income... is a month of study to be essentially among the most paid people in the world REALLY such a horrible thing?
At least for doctors this isn't universally true. There's continuing education/certification, (which you have to do every $period) there's public reputation, there's lots of networking. From what I've seen the interviews take few hours in one day and people usually already know each other.
I'd much rather deal with whiteboard interview bullshit a few times in my life, then go through residency in the medical field.
This has nothing to do with how programmers are hired, and everything to do with the business cases that building software serves. Even if programmers were hired like doctors, they'd still be cyclically losing their jobs, because their jobs are closely tied to the willingness of the economy to spend large amounts of money on custom software.
If you want a job for life, then you want to be in a profession that does something unconditionally useful. Healthcare, garbage pickup, teaching, farming, being a janitor. We're going to need people doing all that long after <insert Silicon Valley fad of the month> is dead and buried.
https://www.alphr.com/business/1005261/silicon-valley-swipin...
https://www.statista.com/statistics/273744/number-of-full-ti...
https://www.statista.com/statistics/219333/number-of-google-...
I have to do a little more to satisfy the process, of course, but I'd be more satisfied if more interviewers didn't just accept the process (as you kind of have to do as an interviewee if you want certain jobs) and continuously asked themselves how they can make things better within their own influence. I could only throw up my hands and sigh when a coworker asked me for interviewer advice, we had a big discussion about interviews, and in the end he just grabbed a random problem off some interview problems site that he hadn't even tested if he could solve himself in the time limit and gave that.
too-strong fear of a
lying false positive
You might be a bit optimistic here: it's not always easy to deal with "lying false positives". Depending on the
legislation it may be difficult to fire somebody, and involve going to court, sometimes going on over several years.
Vindictive personalities may engage in sabotaging the company, the team, their (former) co-workers, as
a retaliation for being fired.
(Anecdote: I have witnessed all of the above in my work.)Summary: the cost of a false positive almost always outweighs the cost of a false negative.
And any company that has thought about their hiring process for more than 30 minutes will have a probationary period of 30 or 60 days or so, after which employment can be terminated if the employee is not able to do the work.
def matches(pattern, s):
if len(pattern) == 0:
return True
c = pattern[0]
assert c not in ("*", "?")
if len(pattern) > 1:
if pattern[1] == "?":
return (
len(s) > 0 and c in (".", s[0]) and matches(pattern[2:], s[1:])
) or matches(pattern[2:], s)
elif pattern[1] == "*":
for i, d in enumerate(s):
if c not in (".", d):
break
return any(matches(pattern[2:], s[j:]) for j in range(i, -1, -1))
return len(s) > 0 and c in (".", s[0])The minimum length will be the number of dots without a quantifier (i.e. exactly one character). If there is any dot followed by an asterisk, there is no maximum length. Otherwise, the maximum length will be the minimum length plus the number of dots followed by a question mark.
Writing the code for this is left as an exercise to the reader. ;)
Knowing that yes, you master compilers (that's usually quickly determined, potentially fast enough for you not to notice it since you live and breath compilers), have basic knowledge in smashing together enough html tags to build a simple dashboard but you never had to deal with processes that spanned multiple computers, allows more flexible allocation:
Ideally, they'll give you a compiler related task, but if they find someone even more suited for that one open position in compiler internals, they might offer you a job in the adjacent compiler-as-a-service team where you'd start out doing dashboards and then move to whatever more complex task needs work.
But they won't need to bother offering you the distributed systems position that scales up the compiler-as-a-service product across the whole world without sending you to some training first.
The job opportunities are definitely out there, but many of them really require a referral (the JDs aren’t posted), and even then you might have to do a generalist interview because the company is not capable of doing anything else.
Here's another one: when does the abs operator return a negative number?
I'm thinking the former without checking now.
Meanwhile, my last project has been to set up an entirely self hosted CI/CD pipeline using digital ocean, docker, jenkins, gitea, and docker registry to make changes to my websites I build with erlang, react, html and sass, so I _think_ I can create projects! (No guarantees).
The interview process is tough, and what do you want to root out more false negatives or false positives? It may depend on the size of the company. Google can probably shell out a few bucks to some putz who sounds impressive but isn't in the hopes they'll nab a few more great engineers at the loss of a few paychecks.
An early phase startup may not have that luxury.
Edit: must be tired since just thinking about fizzbuzz for two seconds clearly gives me the answer to what modulus returns ;-)
They actually take the opposite approach. Supposedly there is compelling research that low-performing members of a team provide large negative contribution to team performance from knock-on effects of their low standards and low quality work. Google has consequentially structured their interview process to minimize false positives rather than false negatives so as to minimize firings and the associated psychological stress caused by working in an environment in which people are regularly fired.
The point of fizzbuzz though is to make someone create a very simple algorithm on the spot. In my experience, there are some people in this world who simply lack the ability to structure their thoughts and plans into a complete set of ordered instructions. That's why you sometimes find recipes online that follow a structure like:
1. Dice the onions
2. Brown the mince for 5 minutes
3. But first, add the onions and tomato paste to the mince
It's the same personality type that cleans a room by walking backwards and forwards to the cupboard of cleaning supplies as they need them rather than grabbing all the cleaning supplies they can predict needing first.
Now, everyone does these kinds of things to a certain extent, but you can't program anything significant if you can't drop into an ordered mindset on command. Fizzbuzz tests your ability to do that without requiring you to know any apis or frameworks or computer science or even a programming language, since you can just as easily do it in psudocode.
http://weblog.raganwald.com/2007/01/dont-overthink-fizzbuzz....
Because cheap stuff you can run away with on 1mil users suddenly falls apart when you need to serve more across continents and suddenly you kinda need to know what all those words in documentation actually mean.
Also, as for CV, everytime I've interviewed people I've gotten more than I few people that lied in their CVs. Persumed "senior developers" who couldn't do a fizzbuzz in their chosen language and tooling. CVs are utterly worthless from interviewers perspective - there will always be someone with exact same CV like you have but will be utterly incompetent.
It’s a relatively simple project with a skeleton of a class and failing unit tests. They have to fix the code to make the unit tests pass.
If they get through that, I give them a second set of failing unit tests that they have to make pass by fixing the class without breaking the unit tests.
But, just because a company gets big, doesn’t mean that you can take hiring less seriously. You still have to be sure that you hire the right people. A false positive - hiring someone that can’t do the job - is worse than a false negative - not hiring someone who would be a good fit.
- There are usually HR policies around firing people that takes awhile and a lot of paperwork.
- You open yourself up to lawsuits whether they are successful or not, it still a hassle and has costs.
- you increase the amount you have to pay to your states unemployment insurance fund.
- It puts a chilling effect on other employees. They think they can easily be fired to.
- if the employee is really bad, they do “negative work” and put more work on the other employees who have to work around them or redo their work.
Very rarely will one employee that you don’t hire make or break an established company.
Everything I know about management, hiring, firing and organizational theory comes from the Manager Tools/Career Tools Podcasts.
As far as hiring, this is my go to guidance.
https://www.manager-tools.com/2007/04/effective-hiring-set-t...
Also, fizzbuzz isn't anything you really need to study for (certainly not for days or weeks). It's something you should be able to work out during the interview if you truly have developing experience. But then again, I've known people with amazing resumes who couldn't even understand the fizzbuzz question itself.
One data point... Senior engineer that founded the local java user group and wrote a published book on the java language. Couldn't code a simple reverse string algorithm, nor explain whether, after with help devising an answer, the method was thread-safe.
Another data point... A self-described expert in SQL with it all over their resume. Couldn't write a simple join, inner outer or other.
Weed-out questions exist because our industry is flooded with people who don't know, nor care to know, their craft. And there are plenty of employers who continue to hire these people, and promote them. I interviewed numerous "architects" (with development experience all over their resume) who couldn't come up with a naive solution, let alone the optimal, to a very simple problem. Want to fix the interview process in our industry? Figure out a way to weed out the liars? I'm all for it. I would rather not have to do basic algorithm questions, but that's the current environment.
It would be unreasonable for me to pass them through an interview that the other members on the team passed through based on "oh, they had a bad day".
Since you haven't been on the other side of the table, have you had coworkers who obviously were at a position above their skill level? Who allowed the rest of their team to carry them?
I've had periods wherey personal life has affected my productivity. That doesn't preclude my ability to write an algorithm that reverses a string nor write a simple SQL join. I don't ask brain teasers. I ask questions related to what the engineers under me will be expected to solve every day.
Also, are your people actually reversing strings by hand every day? I sure hope not!
I've interviewed well over 300 people, for positions from junior/entry-level to principal. If you read many of the comments to this article you'll hear other people with experience interviewing who also call out that candidates can and do lie. I don't like it, I'd rather it not be the case. I constrain the majority of my questioning to what a candidate claims to know on their resume. Here's a tip... If you don't know it (and I'm not talking about bullshit trivia questions), then don't put it on your resume.
I'm joking. (sorta)
I'm glad to hear that you tailor to the resume, that's actually better than most and my favorite approach.
But if I had a dollar for every time someone walked out of an interview with a braggadocious claim like "they couldn't even do X, they must be lying" but then answer "no" to "did you ask them anything else?". I'd be rich.
Reversing a string is a bad example, it is dead easy. But it seems a lot of people have random substitutions for it of varying obscurity and difficulty.
Just because a candidate fails or falls short in one area doesn't mean they are cut, but it's a pretty large red flag if a candidate purports to know something, both on their resume and in person, yet can't answer some seemingly basic questions. If you state on your resume that you architected and implemented a system end to end, yet can't whiteboard the result and explain bottlenecks or failure conditions, I absolutely will assume you stretched the truth a bit. And if the candidate feels the need to do that to get the job, what will it be like to work with them? Could you trust their estimates? Would you be able to back them if something they delivered fails and you trusted them as a senior to deliver?
I ask follow-ups. I give hints. Honestly I'm dismayed at the skillset of purported "seniors" and "architects", and that's interviewing for small companies up to one of the FAANGs.
Thoughts?
I agree that we don't code in a vacuum. What I'm trying to ascertain in the interview is how someone thinks, how they approach a problem and work through the solution. The more they communicate the better, even if part of that communication is "is there a length property on the String class?"
I note, but don't give it too much weight, if there are minor syntax errors. I ask candidates to walk through their code with an example input, especially the ones that have errors. If they catch their errors and fix them, I note that. If they skip over their errors because they assume the code does what they wanted it to, I note that.
Ultimately, can you reason through the problem, come up with a solution, and talk about the tradeoffs you made in your implementation. Any senior should be able to handle that without any preparation.
I worked at a FAANG where in several loop debriefs I was challenged on the complexity of my question. One of the challengers asks a chutes and ladders question (given a random chutes and ladders board, where you can choose between 1-6 for every move, what is the minimum number of moves to get to the end).
It doesn't take a hard technical question to figure out whether someone knows how to think and work through problems.
Coding: on a whiteboard or with someone watching over you has no correlation with performance on the job.
Data structures: questions usually end up so contrite that they have no bearing to real-world situations. That or based on luck of seeing an remembering the right one. Data structures usually go hand in hand with algorithms.
Algorithms: questions become more like trivia or reinventing something that has likely got research papers on it. Oh, you want me to invent an algorithm I've never heard of on a whiteboard with your clues?
System design and data modelling: the kind of thing you can do in an interview lacks real-world data. No empiricism. It's all about the trade-offs.
Tailoring to the candidate introduces inconsistency and unfairness/luck.
What if these "seniors" and "architects" are frauds?! How else could they hold down a job for 20 years and not be able to answer my questions? They must be really bad!
Lucky my interview process is really great and I always hire the good ones. I track every rejection and I have proof that they never amount to anything!
My policy is to ask about those things instead. The ones you'll actually do rather than the ones that are, at best, tangentially related.
If you can't do that then you should probably worry about your own skills before testing somebody else's.
I lopped off a block of the code, made it run without the rest of the code base and explained what it was supposed to do. This wasn't that simple, but could still be explained in about a minute to somebody with familiarity in ML (assumed; that's what we're hiring for). I then challenged the candidate to spot any bugs and implement a feature.
This really wasn't that hard. I've done the same thing twice before in two completely different industries.
Why would that be impossible for you?
As I read it the main observable difference between your exercise and the kind of exercise you're arguing against is that you are starting with some baseline code that the candidate is supposed to modify. That seems like a pretty good idea, but I haven't used it yet.
That's unfortunate, but logically inescapable.
You were interviewing senior engineers with Java experience and they couldn't come up with Assert.assertEquals("radar",StringUtils.reverse("radar"));
I suspect you were actually looking for the implementation of StringUtils.reverse() and if that's the case then you were focused on the wrong skills.
1) not asking clarifying questions 2) not being familiar with some well-known libraries 3) not being able to implement a basic reverse string 4) not being able to explain whether or not a simple method was thread safe (with multi-threading experience all over his resume)
I expect engineers, senior or otherwise, to be able to write code. If you can't do that, don't put it on your resume.
If you honestly think implementing a reverse string method is "too complicated"...
Edit: sorry, leaving the response as-is, but I recognize you didn't state "too complicated". You stated "focused on the wrong skills". I posit that an engineer that can't reverse a string, as a litmus test, will be likely unable to solve a more complicated problem.
It's not that I think the question is too complicated, just not the best marker.
In my mind, more relevant questions are ones that demonstrate real life experience in the field. For example, populating a tree of objects in a high level language like Java from a DB where the tree of objects are stored as many to many relationships. You'd be surprised how many times I've run across production code which does this via SQL calls inside nested loops.
This whole infatuation with algorithm questions like you'd find in SICP might be good for new grads but misses the mark for Senior level engineers.
I didn't ask them to implement dijkstra's algorithm, or even something as "hard" as breadth-first or depth-first search (which I feel any senior that deals with trees should be able to do).
It's a marker of this... Can the candidate solve a basic problem? Once they solve it, can they explain their solution? Do they understand the memory/time tradeoffs they chose? Do they know whether the code they wrote is thread-safe? If you don't feel a senior engineer should be able to answer those questions, to a very basic problem, how do you expect them to tackle something more complex?
As for the interview itself, well I've never needed to ask someone to reverse a string to determine if they're going to be of value with the criteria mentioned above.
But to be fair I've never worked on a project where implementing StringUtils.reverse() was required. If I were interviewing someone to work on Apache Commons or the JDK then I suppose that would be a relevant question.
What I'm interested in from a senior engineer is how many systems they've designed, implemented, deployed to production and supported in their careers and what their specific roles were in those projects. If I can't get an idea from their resume I wouldn't contact them for an interview.
And when their resume looks good and claims they are an expert, and you call them in and talk to them and they say they are an expert, and you start by opening a warmup question on the most basic levels of their expertise and they totally flunk it on multiple levels - unable to even handle the situation with tact or diplomacy in any way, are you still going to trust what they say about the systems they've "deployed and supported"?
usize len = strlen(foo);
char* bar = malloc(len);
for (int i = 0; i < len; i++) {
bar[i] = foo[len - (i + 1)];
}
and explain why that won't work for unicode strings, I imagine, would pass that particular fizzbuzz test. Bonus points for pointing out the null byte off by one error.The only competent programmers I can think of that wouldn't be able to come up with that off the top off my head work in embedded or FPGAs where strings are rarely relevant.
And yet, despite how easy the question is people still fail it. It's frankly absurd to me that a senior software engineer can fail this question. It's practically a freebie slam dunk for anyone with basic competency. Briefly drop that you can use your language's core function or method to do it. Then declare a new array and iterate through the string backwards, appending each character to the new array. When you're done, collapse the array to a string.
In other words, it's testing if you can write a for loop. How many times in your job do you expect to implement a for loop? I use for loops quite often.
What about multi-byte characters?
If you were interviewing with me, I'd ask you to do the (usually expected) ASCII/array-of-graphemes version first. If you did that, you'd pass, and get a positive shout-out in the feedback session for asking about multibyte chars.
If you, after solving the array-based form, had some ideas or even working code for how to handle multibyte characters directly, without falling back to the standard library of $language's idea of "what is an iterable character-equivalent unit in a string", and demonstrated similar insight in your other interview problems, I'd give a positive shout-out with the addendum that we might be interviewing you for the wrong (too junior) position.
In my experience, most people don't ask about multibyte chars. That's fine, if they solve the problem. It's not a positive or negative. If an interviewer is building questions with hidden "must-ask" gotchas like that, I think they're doing themselves and their candidates a disservice.
Something interesting does happen occasionally when candidates do ask about byte-width (or equivalent less-common but still very important gotchas like pointer/word size, endianness, etc. in relevant problems): some people ask the question, solve the naïve form of the problem, and then offer some thoughts as to how they'd handle the broader multibyte case. But some other people act as if knowing that gotcha means they won't or shouldn't have to continue solving the problem. I've had candidates tell me that they "figured it out" and wanted to go on to the next challenge at that point, without writing a line of code. I've had candidates tell me flat out that writing non-Unicode aware string processing algorithms was unrealistic and a waste of time, and that they wanted a problem that was more real-world or suited to their level of skill. Those things will also get you a shout-out in the interview review session, but not the good kind.
a. You can't iterate a 'String' backwards. You need to know the length first. And that requires traversing the string forwards at least once.
b. Once you reach the end you are wasting the effort of revisiting the elements, since you visited them already once.
c. A better option is build a build a double linked list, as you are traversing the list forward.
d. Once you have the double linked list ready, you have pointers to both start and end, and you traverse the way you like.
e. An even better way would be to design a data structure that contains all this meta data at String creation itself.
Class CustomString {
char* headPointer;
char* tailPointer;
int length;
bool isPalindrome;
char* string;
/* Add your interview acrobatic things here */
}
Stuff like this.Now even though the answer in your comment is correct, they could reject you for not coming up with the answers I gave from point a through e above.
Now imagine some one telling you that, on these grounds, you don't know a semicolon worth programming and are probably a liar.
I hope you understand what's going on here. Every body can be rejected if they don't cut through your cookie cutter.
That's not at all true in many languages. If a candidate asked "is this string's length known without an O(N) operation on the number of characters in it?" (or knew the answer for the default string constructs in the language they were using for the problem) I'd consider that a positive indicator. If they said what you just said, without consideration for the context, I'd consider that a negative.
This is not a case of someone expecting a given "cookie cutter" solution. Interviewers who do that are doing themselves and their candidates a disservice. This is a case where statements like "I know how strings work because I know how they work in $context" where $context is not what the interview expects you to work in will make a bad impression.
In an interview, there is an unspoken assumption that you won't be using third party libraries to implement algorithms, and certainly not a third party library that implements it in one function call. Using that as a red flag will yield a LOT of false positives.
Also, I have over 10 years experience in Java, have used Apache commons extensively, and had no idea that a string reversal method even existed. You can't use that knowledge to judge anything useful.
A fail is not a red flag. A senior candidate not asking clarifying questions does not disqualify them (what I would call a red flag) but it is brought up in the debrief as a potential gap. I don't expect them to state this could be implemented using a single call to Apache commons. I call those candidates out in the debrief as being aware of the library, as a bonus. But not saying it isn't a negative.
They may exaggerate claims - yes, that is why you gave them a call in the first place. But then again you exaggerated your claims in the job posting of which skills are required for the job.
The one thing that I noticed is that only the US companies have this awkward parallel reality 'technical-interview' hiring process. In other countries like Germany or France the interview process is mostly focused on the person and the desire to work for the company and the willingness to learn the skills needed for the job. Just because you fail to answer immediately to a random question it does not mean you are unqualified for the job.
When I conduct an interview I try to only ask open questions like: * What is your favorite IDE? - Whatever the person answers, tells a lot about how he works, what tools he uses, and if he is aware of the common tools * What feature of the new Version of <Programming Language> do you like the most? - A) you may learn about some weird feature, b) you can discuss how that feature will improve code * Do you prefer JavaScript or TypeScript (dynamic vs typed language)?
There is no right answer. It is all about how the candidate argues his answer. You learn more about the person and if you can deal with him on a day to day basis (and if he has the brains to think about things).
There was a blog post "Adventure in the Low Status of Software Engineers" by Michael Church (apparently taken down now), basically if you're interviewing for "low status" positions you're assumed to be a fraud but for "high status" positions (VP-level) you're assumed to be a great candidate even if your resumes are almost identical in both cases.
In my experience, firing someone takes multiple months. Months in which they are mutating the codebase (with review, but it's a time sink that shouldn't exist for a decent senior), influencing other engineers, etc.
Passing on a good candidate is cheaper in the long run than hiring a bad candidate. Or said another way, false negatives are preferred over false positives.
> You would be astonished how little people lie on their CV.
This has not been my experience. From something as white-lieish as "I designed and implemented" vs. "I was a peer on the team that did it" to flat out fabrications. You learn alot by simply asking "what was your role on the project" and asking follow-ups to dig into their contributions.
Don't most companies have a probation period these days.
That is no doubt your experience, but I assure you it is not universal. I have heard, and in some cases personally seen, some truly shocking things!
> In other countries like Germany or France...
Perhaps the gold digging nature of Silicon Valley entices far more scammers to cook up a SWE resume and roll the dice, but I think it's a very different hiring world here.
Really, it's not fizz buzz or string reversal that causes people to re-study for their algorithms and data structures exam before an interview.
In many ways, I think this is similar to requiring that senior actuaries re-study integration by parts prior to every interview. They don't have to, because they have a proper exam that is widely accepted in their field. We don't. So instead, we are taken through full day whiteboard exams, under conditions of great secrecy, over and over, every time we interview.
Like this is it. As good as it gets.
I actually think all this back and forth, chopping and changing, people arbitrarily weeding companies out, companies arbitrarily weeding people out is providing just the right amount of randomness for everyone to wind up somewhere.
Hiring is mostly random.
Other hand, I'd suggest instead of "lying" that people are just myopic about their skill sets. I'd been writing JavaScript code for years, for example, but on an interview learned about a whole world of "modern" JavaScript that I didn't know existed. Clearly they thought I was a fraud. But I'd just been living on the 3rd floor without ever visiting the basement where all the pipes and boilers were.
1. Make sure you actually know what’s on your resume
2. Make sure you have the strategic thinking and interpersonal skills to own the system you’ll be working on
3. Make sure you’re a good match for their fairly unique work culture
After about 5 minutes of this I literally said:
"Dude, have you seem my resume? I literally built a petabyte scale full text search engine and wrote 1.5M lines of code to do so and a HTTP framework that parses fetches more than 2PB of HTML per month. If there's some edge case that I might miss I can Google it in 30 seconds".
I no longer keep small tactical issues in my head. It's pointless. Now I try to understand the system as a whole.
Or they could just be asking gotcha trivia. It’s hard to tell.
;)
It sucks, but this is what happens when the job you’re interviewing for has no license or certification requirements (but pays six figures).
But in most cases. Its not very difficult to write 1.5 million lines of code for any project if you are writing code of the style AbstractClassFactoryFactorySingletonDispatcherFacadeInitializer
That sort of the code is basically 90% auto generated by the IDE. You write the remaining 10%.
As a matter of fact I would find it a tad little hard to believe that some one wrote that much(1+ million LOC) and didn't find a way to template it or do some metaprogramming work.
Patterns always emerge from that kind of pile.
I don't think a developer would write a million line at work in their entire lifetime.
I'm not saying it's impossible to achieve. I've seen outsourcing agencies deliver 100k lines with just a few block copy/pasted many many times, but that's neither working nor maintainable software.
1.5M lines is the output of a team of hundreds of developers over years. I don't believe anyone would write a million lines during a job.
2PB a month, is 125B documents at 16kB each, or 50k documents per second. That's decent. That's where it starts to be interesting in elasticsearch or hadoop.
About 200K lines of code is auto-generated.
A more appropriate estimation would probably be about 400k lines per year as some of this code did a big mass migration and refactoring during this time but I wrote that code as well. Just in the past.
KLOC is a shitty metric anyway.
I'd rather write 100 KLOC that worked vs 10000KLOC that was horrible.
I would like to speak to this after interviewing at a few places recently, including Google. I don’t think a single interviewer looked at my resume. I’ve developed a sizable open source project that is used by real people for over a decade. If the company really wanted to know if I could write code they could just go and look at it. Instead they ask puzzle questions that I have no interest in and end up failing. These companies expect the candidate to spend weeks preparing for their hoop jumping, but can’t be bothered to actually read the CV. Multiple people didn’t seem to realize where I lived even when my address was at the top of the paper.
That's bad interviewing.
I can do the problem easily without someone looking over my shoulder, and I need more than 10 minutes just to think about the 8 or whatever rules he gave me.
He failed me, and I ended up working there anyway a year later after the guy quit (true story).
The changes that I particularly like are: improvement in coordination between interviewers themselves, and stop sharing feedback between themselves until the very end. The latter really affects how next interviewers view the interviewee.
[1] https://blog.usejournal.com/rethinking-how-we-interview-in-m...
We've found we're a lot more accurate because we don't influence each other, as well as don't go into autopilot on an estimate assuming someone else has it under control, or someone just deferring to the more Sr. Dev when the more Sr. Dev made a mistake.
I could see how this would also work well with interviews.
LOVE IT.
I think best when I have a chance to actually think, not when I’m participating in some odd job interview game show.
> Our dev teams had taken to working with candidates to solve a bug or feature as part of the interview process. It was a collaborative effort with the candidate and the team working together to solve a real problem.
Sounds like a great idea.
Except it's so variable. What if you get lucky and you get a easy bug, whereas someone else gets something much harder. Let's standardize that by giving everyone the same task to work on.
And what if we want to hire people who aren't fluent in your project's programming language? That would be a big handicap for them. Let's deal with that by having minimally sized "projects" in all the languages, and allowing the candidate to choose their preferred language.
And we don't want the interviews to be biased against people who don't already have domain knowledge in a specific field. So let's make the task generic enough to be approachable by any good programmer.
Congrats, if you did all of the above, you've reinvented leetcode style interviews.
There's some cool stuff that MS has put into practice. I like the focus on reading/understanding existing code, instead of just writing code. I also like the relaxed pacing and "open book" approach.
But for the most part, I don't think this is really as revolutionary as people think it is.
This is unethical. How is this anything other than unpaid labor?
It’s like getting a free sample of food at the store, before committing to a full purchase
Absurd.
Imagine being a programmer applying for a job and not being asked to demonstrate your skills at interview. The interview goes well, and you're offered the job.
You give your 4 weeks notice on your existing job, and turn up to your new role. You sit down, it's day one, and you're presented with a small sprint of bugs to work through to get warmed up on the project you're assigned.
Your heart sinks.
You realise that you are totally out of your depth. The solution you're working on is hard, the documentation insanely complex, and you feel more and more despondent as the week goes on.
By the end of the week your colleagues and managers have started to pick up on your struggles. Despite their effort to help you can't make meaningful progress. To cut a long story short you're let go, and now you're unemployed.
-THE END-
As an employer and owner of a software company, it's my job to assess the skills of somebody as quickly and efficiently as possible. If getting them to "build a small bedside table for free" gets both me, my colleagues, and the candidate attending the interview comfortable that we're offering a job to somebody who can succeed at my company, then so be it.
Your story is only possible if the interview process failed miserably. If your process sucks and results in a lot of false positives, that's your problem. Don't use it as justification for milking candidates for unpaid work towards actual deliverables.
Probation exists to be used only extreme circumstances, not as a catch all for "hey, sorry we made the wrong hire". It's more expensive to hire a candidate and kick them out on probation than to avoid making the wrong hire. This is another reason my approach works - we don't "milk" free labour, we don't need it. Our interview ensures we make the right hire first time, every time and part of that process is some "real" work.
Our interview process is awesome. Refined over a period of 10 years. Candidates learn something, we learn something, we collaborate with them. We often have candidates, even those who do not receive a job offer, compliment us on our process.
I'll write our interview process up one day and share it on HN so others can benefit.
My thoughts on Redmond were that it rains all the time and the inside of the Microsoft buildings is pretty depressing.
I caveated I know networking better than most but I'm by no stretch a network engineer. They agreed and explicitly stated the position was on the systems side and it was fine.
The interview was only an hour and half. About 30 minutes into they ran out of questions and started to get bored. They tell they're all studying for their CCIE's and decided to start borrowing questions from the final exam.
They decided to play "lets stump the Cisco guy". And did they? YES! Did they stop? NO! This was 7+ years ago and I'll never forget how uncomfortable and bad that interview was. They managed to dredge up all these arcane, stupid questions, some of which bore no practical function.. and listened to me "I dont know" for a solid hour
I'm sure it left them with a bad impression of me, and it certainly left me not wanting to work there.
maybe I'm reading too much into this but ... for some reason, none of these questions are highly programming-centric (e.g. implement a sort algorithm, build a B-Tree, or even just implement the singleton pattern in C#, or whatever). all of the questions are human behavior-centric. and I wonder if maybe Microsoft has concluded that the really important challenges are not technical challenges, but marketing ones.
>(Note: I started at Microsoft when we were still asking questions about why manhole covers were round, how many ping pong balls would fill a 747, and how to reverse a linked list. In 20 years here, I’ve yet to have to write the code to reverse a linked list (copy-paste anyone?) or fill a 747 with any kind of ball.)
The manhole cover question is actually a valid industrial design or UX question even if it's not appropriate to ask for software interviews. The linked-list question is the equivalent of Fizzbuzz for data structures. And the 747 question is a valid Fermi problem. The exact number doesn't matter but the steps required to estimate the answer are similar to other estimation problems when mapping out a business strategy and trying to determine if it's profitable. Or maybe the company is interested in salvaging sunken planes: https://www.iusmentis.com/patents/priorart/donaldduck/
PS: At ~250 lb you can see why a less optimal shape might be a problem.
Reasons for the shape might include:
* A round manhole cover cannot fall through its circular opening, whereas a square manhole cover might fall in if it were inserted diagonally in the hole. The existence of a "lip" holding up the lid means that the underlying hole is smaller than the cover, so that other shapes might suffice. (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture.)
* Round tubes are the strongest and most material-efficient shape against the compression of the earth around them.
* A round manhole cover of a given diameter has a smaller surface area than a square cover of the same width, thus less material is needed to cast the manhole cover, meaning lower cost.
* The bearing surfaces of manhole frames and covers are machined to assure flatness and prevent them from becoming dislodged by traffic. Round castings are much easier to machine using a lathe.
* Circular covers do not need to be rotated to align with the manhole.
* A round manhole cover can be more easily moved by being rolled.
* A round manhole cover can be easily locked in place with a quarter turn (as is done in countries like France), which makes them hard to open without a special tool. Lockable covers do not have to be made as heavy, because traffic passing over them cannot lift them up by suction.
I also think the casting argument is a good one and its a lot easier to cast a round object than a square one (its to do with how molten metal flows)
Making a manhole cover round is one of the first intuitive shapes you'd think to make them (along with squares and rectangles); and so you'd guess, as a construction company gearing up to sell the concept of concrete manholes with removable iron-plate covers to a municipality (back in the 1800s or whenever we first got them) that what the municipality will ask you to make is round manhole covers. So you provisionally set up your tooling for round manhole covers, and build a few for the demo. And the municipality assumes you're the expert about good manhole-cover shapes, and so just goes with the flow, rather than trying to figure out the best shape themselves. So you end up with "the first intuitive thing that worked" spreading via network/"system compatibility" effects.
Same with road widths; same with screw drives.
Which is why the "Robinson" screw head was invented (Canadians are immensely proud of this one)
https://en.wikipedia.org/wiki/List_of_screw_drives#Robertson
If you already know the answer, your main problem is acting like you're thinking it through.
So they reckon a 45 min quiz/chat is what will tell them who to admit.
Gets pretty open ended, favors people who can talk well.
I ended up not applying to MIT because you get your acceptance before Christmas and the US applications are huge. But my understanding is the US school interviews are more cultural fit?
So imagine how a candidate reacts to, "Well, while we know you're happy where you are, what would you think about quitting your current job so you can try out a position at our company for a few weeks?" (Note that candidates can't use vacation time just to do a try-out, for legal reasons, and may be reluctant to use up all their vacation time in any event).
Having a trial period puts all the risk on the candidate, and guarantees you're filtering out people that you'd otherwise want.
They wanted monte carlo (more darts, more precision), I went riemann sums (smaller delta x, more precision). It totally through me off my game for the rest of the interview as I was constantly thinking about it.
while not quite a traditional brain teaser, there are a couple of insights one has to get to solve it
1. ratio of circle area to square = pi/4 (but remember, you don't know pi yet, just that it exists, the point is to estimate it)
2. a way to make use of that ratio (i.e. monte carlo, pick a random 2d point (on both x,y from -0.5 to 0.5) if the distance from (0,0) is greater than 1, it is only added to the square, otherwise it gets added to both.
combine the 2 insights and you get pi ~ 4*circle/square
(as mentioned I went with riemann sums, where I calculated the area under the curve of the circle's arc in one quadrant, but same idea you get pi ~ circle_arc_area/.25)
those 2 points aren't quite obvious (I went riemann sums as area questions made me think calculus and went totally down that rabbit hole), and in 30-40 minutes of brainstorming (first 10-15 minute discussion about the person, then actual interview question, then 5+ minutes for any questions you have for the interviewer) can be difficult for many people to get.
The problem can then be, many people can't just stop thinking about a problem they struggled with and will continue to process it (hurting their following interview Qs),
i.e. even if that interviewer thought I did sufficiently, I believe it hurt me on the following Qs as I couldn't just let it go, which in the real world is how I think many people work. If they are struggling with how to solve something, they are dealing with it even when they are supposedly focused on other things (say in meetings, eating lunch....)
If it's a "brainteaser" is I guess a matter of definition.
Look, I'm sure people are asked bad questions at all times in all companies, but the policy at Google was clearly to not do that. At least when I was there 2006-2009.
Of course I know right answer, but it has zero to do with me being smart and a lot to do with me being in right culture and thus having heard about it before. Which is exactly what it test along with other brain teasers - have you encountered this sort of question before?
I personally hate this kind of interview question. It’s one that is easily answerable when one heard the exact question before (in training for interviews). But super hard to answer if not. And it even does not have big applications in practice - in 20years of programming, I never encountered a problem like this. In the end the question just wastes time on both sides and won’t really tell a lot about the candidate.
I too got this question at an interview once, and failed. For fun I asked everyone at work and predictably nobody came close to figuring it out.
Marking items visited can actually work, because on any(?) modern OS the memory for the elements in the list would be allocated at even addresses, meaning the low order bit of the Next pointer is always zero and can be reused as a marker.
If you've never seen the pattern before, there is a very good chance that you're hosed.
Edit: found it [1]
[1] https://en.wikipedia.org/wiki/Cycle_detection#Floyd's_Tortoi...
For me it wasn’t a pass/fail “do you know the right answer” question, it’s more of a “can I work with this person” question.
In constant memory there's not that many things to do, a single pointer clearly won't be enough as you can't recall if you already visited the node or not, so `K>1` pointers must be used. If any two pointers moved at the same pace they would be duplicated and the second won't give any information. That and the fact that you can only move forward leaves a pretty constraint situation and acts as a guide.
It's not a bad thought problem, but I guess the fact that it's really unlikely to happen in a real world scenario plays against it (the memory on a hash table is probably way cheaper than the extra reasoning this takes). Also, knowing a bit about the answer is an unfair advantage, it might be more of a test on memory than on reasoning, which makes the problem bad for interviews.
It is one that a lot of people will go "Aha, of course" when they hear about it but not figure out themselves.
I think a better question might be, "tell me how you've mapped out a business strategy in the past, and what are the strategies you've used to determine how profitable it would be".
These anti-skills will have been used quite regularly at Microsoft.
The process that my CTO and I have found works best is as follows;
A 20min phone interview (to screen for BS’ers).
A technical test that’s based on the sort of problems they will be solving in their job. How would you do X in language Y, no boiler plate code, and it doesn’t have to be perfect. (So no fizz buzz, conways game of life etc.) We also stipulate to spend no more than 2 hours on it, and if their successful they get that time back. We even offer a discount (on the thing we sell) to unsuccessful people who don’t make it. The test serves as not only a good high level demonstration of ones skils but, more importantly, gives us all something to talk around. It also shows us how they approach key things like testing, deployment, maintainability etc etc.
Then there is a 2 hours face to face interview. Ahead of this the test is peer reviewed by the engineering team (or part of it) The interview is made up of one one hour technical section with the CTO/Senior, and one with a designer/product manager. A joint decision is made.
Then, if they are successful, we have a probation period where we (the candidate and us) work out if it’s all going as we’d hoped. If not, we part ways. You most likely wouldn’t marry someone before a first date. A job is the same. You both need time to see if you like each other and your profile pics match real life.
It’s not perfect, but no system is. Sure we’ve hired a few people we’ve had to let go, but for the most part it’s a great system. We’ve managed to hire not just great engineers but also build a team and culture that fits and works.
Hiring is time consuming, hard and at times emotional. There is no shortcut.
I’ve interviewed and worked at big tech companies and they all think there is some secret sauce, a magic code to hiring. That is, if you ask super hard questions only the “best” make it through - utter tosh. Some of the most amazing engineers I’ve worked with would fail these type of stupid questions (for a while load of reasons) but quietly write amazing code.
Also, and more importantly imo, to be an amazing engineer you need to be great (equally) at teamwork and communication, not just be super book smart.
I read a while back (or imagined it?) that MSFT only hired people with Msc’s/PHd’s and that it created a probelem where there wasn’t any intellectual diversity. These tests cause this too. You get cookie cutter people who are smart but often can’t work in teams and can’t communicate well.
Please don't. I can take one day off work for a full-day interview; I'm not going to burn through four fucking vacation days for you to vacillate over whether or not I'm a "culture fit" or whatever.
Depending on what you do, maybe most of the time interview-like problems won't rise up, but not everyone is ok taking the risk of poor algorithm design on production. While it won't happen that a single engineer will need to do everything without any design or code reviews, if you keep "lowering" the bar you risk breaking the review failsafe. Maybe scaling the review process can enable teams having more engineers working "safely" as the hard problems will still be reviewed by the "elite" engineers those companies try hard to get.
I hope this takes some pressure away on pretending to have "real" interviews needlessly. There's too many problems to be solved out there to be overly picky on who can work on them.
It would be nice to hear back from MS after they a few years.
I’ll go first, because I’m quite sure I’ll win...
This was for a front-end mid weight software engineer position. The candidate was smart and a 100% hire (I’ve since hired him 3x in different companies)
Me; “great thanks for your time and we will be in touch later today”
Co-interviewer; “I have one more question”
Candidate; “sure, go ahead”
Co-interviewer; “Imagine your uncle has just died and left you his pizzeria in his will, what would you do?”
Me; “what?”
Candidate; “what...? Errr... sell it because I’m a software engineer, not a pizza chef”
It's ironic considering how MSFT pioneered the original brain teasers/problem solving questions.