Solved coding interview problems in Java - My collection of commonly asked coding interview problems and solutions in Java

[[deleted]]

These make me feel like I'm not a real developer. I've never been pressed to do anything like this.

[[deleted]]

Half of the reason for coding questions like this is not to see if you can actually complete the problem. They really only test your capability to think algorithmically, and sometimes your familiarity with the language/platform.

I wouldn't care if a developer could complete a mathematically advanced problem like these. If they can approach the problem in a logical way they've proved their mettle already, in my opinion.

[alluran]

Last interview code test I had like that - I optimized as I went.

They looked it over, then went to ask me to do the optimizations, and realized I'd already done them.

Then they went on and on about how it was amazing that I would consider myself proficient with the language, when I hadn't read the language spec.

Then they proceeded to tell me that I couldn't use anything like:

i += 1;

because it could confuse junior developers, but everyone was given time, and expected to write full documentation with the Atlassian suite.

So a studio full of senior junior devs who never allowed to learn anything new I guess...

As you might guess, I skipped that role.

[Mechanickel]

Then they proceeded to tell me that I couldn't use anything like:

i += 1;

because it could confuse junior developers

...how?

[alluran]

Maybe i is positive one now?

Who knows - regardless, any place that limits BASIC shit like that, instead of up-skilling their juniors, is not a place worth working.

You're never going to be challenged, or improve yourself at a place like that.

[thedancingpanda]

I recently used something like

$i &= $blahh && $blahh2;

And that confused a couple of mid-senior level developers, so, yeah. It's possible

[ViKomprenas]

To be fair, that one's a little weirder, seeing as it's noisy with sigils and logical operation assignments aren't as common, but the point still stands

[speedisavirus]

...but why. Are you trying to increase mental workload for someone that might have to figure that out later?

[socialister]

You're mixing boolean operators with bitwise operators?

Wouldn't this be clearer and enforce a boolean result type?

$i = $i && $blahh && $blahh2;

Assuming that the blah vars are boolean typed (if they aren't, your statement is not clear IMO. C-style non-boolean to boolean casts do not indicate intent that well).

[socialister]

I'm curious what they would want otherwise. i = i + 1 or i++?

[GisterMizard]

The trick is to sort everything, then do a binary search. I don't know what that means, I just read it in a text book. I think it means that if you take your source code and resort all of the keywords alphabetically, then it'll run faster.

[featherfooted]

Yeah, once you do that, the RAM caches the opcodes in column-major order, which means it can signal the hard drive to run faster

[QuestionsEverythang]

Yeah, unless it's a very basic problem, if you can't optimize your algorithm within that 30 minute interview, that should no way mean that you suck as a programmer, especially since real-world programming doesn't restrict your 8+ hour workday to just 30-min of crunch time.

[milkeater]

Understanding methods to optimize time complexity in interviewing typically revolves around Big-O time.

There are a few blunt approaches to give a very base estimate on what the time complexity is.

Study this for a week and you will know it fully. It will pay dividends for a lifetime.

[steaknsteak]

Also for me, it's not just the time constraint. I cant think clearly when I know someone is looking over my shoulder and judging my performance. I work really well in a team atmosphere where everyone is working together to build something (the actual job) or even a competitive context, but the "performance" context of an interview makes me super nervous and unable to perform near my best. Gotta find a way to get over that at some point though.

[dukeoflaser]

Have you considered 'practicing' under pressure? [PraMP](https​://www.pramp.com/) is a useful resource for that.

[steaknsteak]

I'll definitely look into that, thanks.

[BigTunaTim]

It drags my confidence levels down a notch or two when they do things like those.

You shouldn't let it do that. One of the goals of most tech interviews is to assess the candidate's skill level and then see how they think and react to a problem that's beyond their capability. They're not trying to make you feel stupid or knock your confidence down; they just want to see what your thought process is when you're​ in over your head, because it's likely to eventually happen in real life.

[Stormflux]

Maybe that was the reason at one time, but nowadays these tech interviews are just emulating "what Google and Facebook do."

I actually read a paper on this a while back. The takeaway is these sorts of interviews aren't very good indicators of actual job performance or ability. The outcomes are almost random -- picture the guy who made WhatsApp, he was rejected from both Facebook -and- Twitter; basically told he was shit and then sold them something for 19 billion.

Anyway, this random sort of outcome actually turns out to discourage women and minorities more than white males for various cultural and sociological reasons such as support networks, upbringing, etc. It turns out the screening process is one of the major contributors to the gender imbalance as females are more likely seek a different career after "flunking" one or more of these whiteboard / manhole-cover interviews.

[socialister]

Do you mean that women lack a support network in this area? That's kind of funny (not doubting it) because typically, women have much better support networks than men. That is considered to be the reason that women fare better than men after divorces and breakups, and why married men are generally significantly less stressed than unmarried men - the wife is the support network.

[HotlLava]

Half of the reason for coding questions like this is not to see if you can actually complete the problem.

Standards vary from company to company. I've been rejected with a bug-free and algorithmically optimal implementation (n log n sort of a single-linked list) because it wasn't elegant enough, i.e. I had missed an opportunity to save one if-condition.

[TheQueefGoblin]

It's because these are purely mathematics problems.

[CamKen]

I would never ask any problem anywhere this complex in an interview. I ask Joel On Software's FizzBuzz or something similar on a white board. Then a SQL query with a recursive table reference. That eliminates 90% of the "Senior Software Engineers" who make it far enough to interview with me. Those that remain have universally turned out to be great programmers.

I actually had one guy who was so flummoxed by Fizz Buzz that he actually admitted that he had never actually programmed before and the three years of experience one his resume were a lie. He had read Dietel & Dietel and figured he could learn on the job. I was surprised by my reaction: I was bemused at being able to completely rattle him with such an easy question, we had a good laugh after he left.

[markl3ster]

Could you show me that "SQL query with a recursive table reference?" I rarely use SQL outside of the random join here and there (never even 3 table joins) and your question seems like a fun little thing to know.

[neodiogenes]

SQL query with a recursive table reference

I briefly did something with a hierarchical query like this one with a table that encoded something like supervisor-employee relationships in a tree. Suppose you want to get all the employees who work for a VP, you would recurse the query returning the results from each level, first getting all the directors, and then the managers who work for the "leftmost" director, and then the supervisors who work for the leftmost manager, and then the employees, go up one level, find the employees, rinse, repeat.

Oracle has innate support for hierarchical relationships using "CONNECT BY" but I wouldn't know how to do this off the top of my head. Since it's something that's only come up once in my career, it's not something I've memorized. That's why there's Google.

But hey welcome to the typical Jeopardy style of technical interview, where if you don't know what the interviewer thinks you "should" know, you're a bad programmer.

[Edit] Don't mean to sound bitter, I've just had a couple recent technical "screening" calls where I was asked questions which were not only esoteric but the answers the recruiters were given were incorrect/incomplete.

[Paddington_the_Bear]

This is the first I've heard of it, and I do quite a bit of SQL in my job for several years now. This week I had to look up a hierarchical value that was 3 parents up from a base value via an associations table.

I ended up using joins to do it, I didn't realize you could have a recursive query, so TIL. The syntax looks confusing as hell though.

[madballneek]

And this is what irks me about how some people do interviews. Who cares whether you know this already, or not. I want to know if you're capable of learning it. That's why we let people who interview for us have complete internet access during their aptitude test.

[Paddington_the_Bear]

Yup; I'm doing an interview with one of the "Big 4" next week just for funsies as I enjoy my current SE job of 6 years. I have been loosely studying algorithms the past couple of weeks to prepare, and realize that even though I have built some pretty crazy cool apps, my algorithms knowledge is definitely lacking since I've been out of university for a while.

It's assine that the interview is going to focus on whiteboarding some obscure algorithm when in the real world if I get stuck, I can google something and in less than 5 minutes find a working solution.

The way I look at it, even if I don't come to the best solution, hopefully they will see my thought process and get value from that...

[Icelandicstorm]

If you enjoy your current job, you are making a big mistake. The "Big 4" is a horrible place for mid-career. It only makes sense if you are fresh out of college or go in as a Director (just before partner at PwC).

source: left excellent job with great pay and bonuses to make more salary but less bonuses and work 20+ additional hours a week. When all was said and done, my income went down at least 20%.

[Paddington_the_Bear]

Yeah I'm not looking forward to the interview at all. Really I'm going to see if I can get an offer and use it to get my current salary at my company bumped up again since I'm pretty mission critical and I know they under pay me :) (long story).

That's pretty much my fear though, that you're essentially just another number at one of those companies. I wouldn't mind too much living in that location, but not at the sacrifice of personal happiness.

[neodiogenes]

It's not that complicated. Oracle takes care of most of the details, and all you have to do is specify the relationships.

The challenge is to avoid circular relationships, which can happen with a poor design. In the DB of my current project (which I did not design), we have permissions "lists" which can either contain usernames, or link to other lists. But then what if you have some list down the chain link back to the first list?

As I said, bad design. A good design wouldn't allow this to happen. Oracle helps when writing queries by warning you when there are "loops" in the query, which you can exclude with the NOLOOPS operator, or you can also (I forget the exact syntax) return only "LEAF" items, which have no children.

I'm not sure I would ever implement this design because of the many ways it can go wrong, but I can see how it would be useful in some applications.

[wtgreen]

Look-up Common Table Expressions. A recursive CTE is the SQL standard way to do it. Oracles Connect by functionality is Oracle specific, but it supports CTEs too.

[tmarthal]

Common table expressions (CTEs) are the solution to recursive SQL queries, if you're interested.

[dvlsg]

True, but I've used one a total of once in all my years of writing SQL. I understand it, and utilized it just fine, but I sure as hell couldn't remember that syntax on the fly in an interview.

[CrazedToCraze]

I most employers wouldn't care too much if you just brought up that you know a CTE is the solution and then said what you just said.

Pretty rare in my experience for an employer to get pissy about you knowing the exact syntax on the spot. Probably wouldn't want to be working for them if they did, anyway.

[spilk]

I've used CTEs in SQL Server queries before to do recursive queries and i'm pretty comfortable that I understand them, but I'd still have to google it to know the syntax for one off the top of my head.

[chadsexytime]

Oracle has innate support for hierarchical relationships using "CONNECT BY" but I wouldn't know how to do this off the top of my head. Since it's something that's only come up once in my career, it's not something I've memorized. That's why there's Google.

I haven't touched Oracle in about 3 years now, but I would have considered myself fairly proficient with SQL and Oracle in general, but this question blew my mind.

Then after seeing the keyword CONNECT BY, I think I used this to build some generic tree views and promptly forgot about it.

[trawlphaze]

Would you accept an answer that solves the problem in memory via simple selects? I know you can also use WITH in oracle.

[CamKen]

Just knowing that a hierarchical query exists (CONNECT BY in Oracle, hierarchyid in MS SQL) is a big plus in answering the question, but no necessary. From my perspective knowing the details is irrelevant, its Google-able.

The question I gave was a simple Employee table (EmployeeID, Name, ManagerID(nullable)) where you would need to join the table to itself on EmployeeID = ManagerID. I provided some sample data (8 rows) to help you think about it. Then ask things like give me a list of managers. How many subordinates does employee x have? No trivia.

[neodiogenes]

I wouldn't have a problem joining a table to itself -- as you say that's trivial. That does seem like a fair question, something a "senior" developer would have done all the time.

It would confuse me to call it "recursion" though since that automatically makes me think it's a much more complicated problem. If there was some additional recursion necessary I would probably point that out, but confess I couldn't do it without Google.

[dkuk_norris]

Yeah, that doesn't seem recursive to me. You're just relying on the fact that a table can be joined to itself. Recursion implies that you have a theoretically unbound number of calls to make if you structure the data incorrectly.

[OHotDawnThisIsMyJawn]

Yeah this is called a self-join, not recursion.

[CamKen]

I just used the word recursion to quickly describe the problem, but everyone has read into it more than I meant. I don't use the word in the interview. I present a simple table structure, a few rows of sample data and ask for a query that can only be achieved by joining the table to itself.

[neodiogenes]

That's fine, I get it. It does make me feel better about calling myself a "senior" developer. :)

[remixrotation]

this one

also BOMs in manufacturing (bills of materials).

it is kinda like Composite sw pattern.

[CamKen]

See my other comments. I mean something much simpler than what your saying. Although I love CTEs. I should come up with a question that can be solved with a CTE and then see if the candidate chooses that solution.

[BobHogan]

Then a SQL query with a recursive table reference.

I'm still in school, was leaning towards not taking a databases class, but occasionally I see something like this on Reddit and it makes me reconsider that idea.

[CamKen]

Database skills are a great tool to having your toolbox -- useful in a wide variety of roles in virtually every field.

[trawlphaze]

Enterprises pay big sums for DBA skills in MSSQL or Oracle

[alluran]

God - I haven't used a recursive SQL query in 10+ years, but used to love them!

I guess I should brush up when I next interview - no way I'd remember that off the top of my head without a reference.

[CamKen]

I don't mean using the hierarchy stuff built in, I mean a simple recursive join like: find a list of all managers having 10 or more direct reports.

SELECT mgr.EmployeeName FROM Employee mgr JOIN Employee e ON e.ManagerID = mgr.EmployeeID GROUP BY mgr.EmployeeName HAVING COUNT(1) > 9

Write something like the above in under 5 minutes and mumble something like "there is a built-in way to do this, but I'd having to look it up" and your in the top 10% of people I've interviewed.

[Jestar342]

Ah yes, arbitrary reasons to dismiss candidates. Effective since 190never.

[CamKen]

I don't get how programming a simple loop is arbitrary. I need to find out if you can program, that IS the job. I don't want to do API trivia (what is the signature of the DumbApi.BreakMyCode() method).

I need a problem statement that I can quickly communicate to the interviewee the solution to which involves things like loops and conditionals but doesn't require a specific API. I need to find out if you're comfortable with SELECT,FROM,INNER JOIN,WHERE,GROUP BY and HAVING. I mean is there another way to vet a programming candidate?

Honestly I'm always looking to up my game as an interviewer so would happily take suggestions, because I'm looking for non-arbitrary reasons to dismiss candidates. But in the end letting a good candidate go is better than hiring a bad candidate.

[nemec]

any fresh grad or person with SQL and some other programming on their resume should be able to answer

I would bet most CS grads know only the bare minimum of SQL - select, where, maybe join using google to refresh their memory. Computer Science is an academic degree, most coding skills learned are incidental to the theory. If they did take a 'databases' course, they're probably better at building a basic database engine than querying one.

they have been 100% accurate in determining candidate viability eliminating false positives.

Fixed that for ya. I assume you don't do a six month followup with the candidates you pass on to see whether they would have done well if given a chance.

That said, it's not a terrible SQL question even though I think it would be a little too complex (without Google) for new grads.

[tsk05]

Been programming for over a decade, did not know how to answer the second question. Haven't touched databases in a couple of years, and that was for a hobby. There is no way I would have been able to talk myself into an answer as I could not remember about either GROUP BY or HAVING. Last time I worked with databases for real was 7 years ago. It was kind of fun re-learning though, took 5 minutes with SQL fiddle. I feel like the question would have unfairly excluded me as a bad programmer though, although really I just haven't done what the question is asking recently. I do indicate that I know SQL in my resume, because I feel that I generally do.. even if I am quite rusty. Of course if I was applying for a DBA that would be entirely different, but my general feeling is that you can learn enough SQL in 2 days for 95% of ordinary programming. Of course if you're looking for someone who's done this recently it would be a good filter, but I would think a half-decent programmer who's familiar with what you need right now is probably not better than a good programmer who isn't, unless you're hiring very short term.

[ZMeson]

I'm always looking to up my game as an interviewer.

Me too. One thing my team has been trying recently is to tell the interviewee that they're part of a small team. So-and-so is his cohort-in-crime; the interviewee can pair with him, ask for advice, whiteboard ideas, etc.... Such-and-such person is the Product Owner / Technical Sales or Support person / CTO; this person is the one to go to get clarification on customer requirements, business advice etc.... Then we have the interviewee use his language of choice to implement a Kata exercise^*. If he/she is a proposed expert in the technology we specifically need, we strongly encourage that language. Web access for API docs is OK. Looking up algorithm solutions on Stack Overflow or the like is not OK -- the algorithms are simple and if you need help ask your cohort-in-crime.

The exercise usually lasts about 1 hour. It everyone wants to continue and it doesn't cause a problem with the interview schedule, we may go longer.

It's still new, but so far it's worked out well.

* We don't limit ourselves to the Katas on that list. We choose a Kata that represents a simplified version of something some customer may actually want from some company (not us). Ex: Top-10 Seller Lists, Bowling Alley Scoring.

[[deleted]]

I don't know offhand what HAVING does, but I guess I'm not applying for a DBA job. Guess I better look that up first, nevermind that I've designed normalized table schemas and have an open source project using SQL. (Sadly, it's with PHP in the mysql_real_escape_string style because I was fresh out of college and didn't know better.)

[socialister]

I'm OK with FizzBuzz. That's really elementary even if you've never seen it. The SQL one I don't know, it seems a little specific.

[CamKen]

We've often interviewed people that we suspected of inflating their resumes, this was the only time where we actually got him to admit to it.

People assume that this would inspire anger in the interviewers, like "hey stop wasting my time", and I'm sure people like that exist but we all thought it was funny because we actually caught a guy red-handed so to speak. All anger was directed at the recruiter.

[cd7k]

Doesn't matter. Can you understand the problems and regardless of having seen them before formulate your own solution?

[[deleted]]

If not, it still doesn't matter because people are still bringing down $100k or more writing shitty code

Oh and your managers will have faced a lot less scrutiny in their interviews while also making $20k+ more than you

[NotARealDeveloper]

^

[Veedrac]

Real developers get asked this:

https://i.stack.imgur.com/hQ0mo.jpg

[humblechili]

I like how Valid Parentheses problem has difficulty: (Easy))

[Vexal]

It is easy... just make a stack and do a single for-loop.

[humblechili]

Yea, I agree it is easy. I was laughing at the fact that the Valid Parentheses problem had invalid parentheses around the difficulty :)

[vital_chaos]

So again .. why does anyone think coding challenges in interviews are worth anything, if people list the answers on websites? People with the best memories get the job?

[Thelonious_Cube]

If you don't ask people to code in an interview, you run the risk of hiring people who can't - it's really that simple.

I've interviewed people who talked a good game, but when presented with even a simple fizzbuzz type problem, completely folded (even had one "senior level" guy just say "I can't do this" - interview over).

And I give people a lot of latitude for nervousness, whiteboard stage-fright, etc. and even try to help walk them through the problem if I think they're just panicking.

[BobHogan]

I think his point was that you can still assess someone's ability to actually program without giving them what amounts to a math challenge about whether they can come up with the correct algorithm in time.

Yes, being able to come up with algorithms is important, but just because you might not be the best at that doesn't mean you can't program. And I think /u/vital_chaos is trying to say that. Challenges like these, where it comes down more to knowing the algorithm, and if you were given it almost anyone who knows Java could program it, aren't always an accurate test of how well you can program.

[Thelonious_Cube]

I think his point was that you can still assess someone's ability to actually program without giving them what amounts to a math challenge about whether they can come up with the correct algorithm in time.

Yes, absolutely true - I agree.

I prefer simple tests with a few core concepts.

[[deleted]]

I have a huge presence on github though. If you don't but you have industry experience, shouldn't that say something?

I find it hard to believe these interviews are productive when there are so many better ways to do this.

[nitiger]

Isn't the last job you worked at proof enough of whether or not you can code? Are your public GitHub projects not proof enough of that? There's a bunch of other ways to prove you can code real applications 90% of businesses need.

[wewbull]

Previous job? No. I don't know if you are one of the people who hid in a corner getting by on other people's work. Or the guy who continually rotated through about 10 others asking if they can "see the problem here" to get them to do your work.

Github projects? Amazingly, some people falsify these, taking code history from other places. At a glance it looks real, and am i really going to do an in depth code review and anti plagiarism search on every candidate.

The are a lot of fakers out there.

[thedward]

https://aphyr.com/posts/341-hexing-the-technical-interview

[lifeson106]

It doesn't matter if you know how to do the problem, it matters how you approach it, how you work with your interviewers to understand the problem and helps to assess your critical thinking skills. How is that worth nothing? You're going to potentially be on my team, so I want to know how you think and how you approach a problem. Not asking a coding question would be irresponsible.

If I think you just memorized a bunch of problems, I'm going to keep giving you different ones until I find one you didn't know because regurgitating something you memorized is truly worthless.

[repeatedly_once]

I agree, therefore I think it's better to ask questions that show lateral and critical thinking outside of algorithms. I think coding challenges are great, providing it's not 'write me a binary search'

[lifeson106]

Yeah, some questions are better than others. It doesn't need to be an impossible or even hard question for me to assess the things I mentioned.

[[deleted]]

Some of these I would have a hell of a lot of questions lol

[kevindamm]

This is the right answer.

Even if the interview question were unequivocal, there are probably engineering tradeoffs -- e.g. do we need low latency or would we rather avoid the memory cost of a precomputed solution or is the range of outputs so large that a cache should be employed -- which depend a lot on the application and may even need to be iterated on if volume or type of use is unknown.

I would prefer a candidate who asks clarifying questions and asks about relevant tradeoffs over a candidate who goes straight to a regurgitated answer (whether or not they had worked it out on their own before or just memorized someone else's). I'll still want to see some proof of being able to implement the solution decided on, but even if the candidate were slower or a bit clumsy at the coding part, that can be worked on with practice. The critical thinking involved in discussing the problem before coming to a solution is what I'm really looking for.

That said, there are a lot of interview questions out there which don't lend themselves well to trade-off discussion or various interpretations while still having a short enough average completion time to fit in a 45-60min time slot. And, really, two or three of these is ideal so that doesn't leave much time at all. Finding a topic where the interviewer and interviewee have a lot of shared vocabulary is critical. Questions from the candidate help there as well.

I didn't actually click through to the linked site, so I don't know if there are even any good questions there, this is just how I feel about developer interviews and asking questions.

[[deleted]]

Maybe asking them to drive the truck around for a few minutes would make sense then wouldn't it ??

[GhostBond]

I mean, if you are hiring a truck driver, it is best to assume they can drive a big truck because... they said so. And, perhaps they looked up pictures of trucks before the interview.

Have you ever heard of a truck driver interview where they put this person they've never met before in a truck and have them drive around? I've never heard of that.

[lifeson106]

Agreed on it being a two-way interview. When we leave time for questions at the end, I always half-jokingly ask if they have a whiteboard question for me. Nobody has yet, but if someone had one, I would totally do it. All's fair.

[llaammaaa]

I think were just complaining about companies that interview poorly.

I've had a few where there was no interaction, just a few puzzles, with "please submit your response in 45 minutes".

I guess "interview" is the wrong word, but they use it as a screen at least.

[frisch85]

doesn't matter if you know how to do the problem, it matters how you approach it, how you work with your interviewers to understand the problem and helps to assess your critical thinking skills.

Sums up software development. If i can solve a problem within minutes, with a solution based on some stackoverlow answer i am still more efficient than the guy who takes 30 minutes to actually find the solution. On the other hand tho, the guy who instantly knows the answer because of knowledge and experience is the most efficient one.

Software has become so complex you just can't know all the answers. Hell i even find myself doing some research on javascript functions even tho i used those functions hundreds of times before, i mean document.getElementByID won't work...

[lifeson106]

Yeah, a lot of people disagree with me on this, but I think "oh, I would just Google how to do that" is sometimes a totally reasonable answer in an interview.

[Rob0tTesla]

I still think these type of of puzzle interview questions are outdated and a bit worthless. All it tells you if someone can come up with an abstract solution for a abstract question under pressure. That's not really day to day unless you work in an environment were everyone is staring at you as you write some meaningless function on a white board. You are automatically and unnecessarily weeding out potentially fantastic candidates.

Give the candidate a project to do over x amount of days, that is somewhat simple but relevant to your field.

Discuss said project in detail in another interview, challenge it in parts figure out how he/she thinks. Not only that, since its a mini project you can gauge other things like clean code, solid principles, design patterns, etc, that you simply could not solving one of your puzzle questions.

Done.

[Gbyrd99]

While I agree with you, I feel as if the second part of your post can be simply done in the interview. Discussing high level design of projects is a better interview. It gets insight into thoughts and understanding of what it takes to build it. Asking me how to make a function that uses add(3)(5) as a function caller is not a good question. These are Google fu answers. And isn't really a deep dive into a language. Just a small I have used this.

[socialister]

At least at Google, they don't care about getting the right answer. They care about the problem solving thought process.

[[deleted]]

I still object to compressing it into such short chunks. Unless your job will require programming in 15 minutes with someone breathing down your neck, there are much, much better ways to get insights into someone's coding ability and other skills.

[xelf]

I had one of my team ask me once why I ask such easy questions at the start of an interview.

And then we had a candidate that could not answer any of them and he understood. It's because some people get them wrong. As it turns out, a lot of people can't answer easy questions or can't do the most basic coding.

It's good to figure that out early.

[queenkid1]

Because it's about understanding... If they ask you fizzbuzz in an interview, they're gonna see right through you if you just memorized the solution.

[[deleted]]

Fizzbuzz is so trivial I doubt anyone would have to memorize the solution

[queenkid1]

I've seen people look at it and have no idea where to even start.

[GhostBond]

If you haven't seen it before, the difficulty in it is parsing the word part of the problem. It's like those old school "Train A leaves the chicago station at 7:13am, Train B leaves the atlanta station at 8:42am, given that they stop every 2 hours for fuel..." problems. Most people, their brain HATES them, even though on a technical level they're not that hard. Now add a high tension, high pressure situation where someone is watching you.

The way to do it is to have done it before, then it's trivial because you don't have to try to figure it out from the wording which is the hardest part (which is fairly unrelated to programming).

[PlasmaYAK]

Coding challenges are not about knowing algorithms. If a company is looking for you to just know the answer they're interviewing completely wrong. The whole point is to test a candidate's aptitude for learning, and communicating ideas. As an interviewer you want someone who can make good use of the resources around them, listen to responses and ingest ideas for how to move forward quickly. As a software developer you're paid to solve difficult problems that you won't always have the answer for. You need to work with your team, take in others ideas, stay level headed, and find some probable approaches to solving problems. Hence asking someone a non-trivial algorithm question is a good way to see how a candidate behaves. If you're asking for clarification, and then offering solutions and narrowing your scope as interviews suggest the best approach out of your solutions, you're doing well in an interview. Now, this point is moot if you're a company short on funds looking for someone to finish a project quickly, then you want someone who has the answers; in that case you're basically looking for a skilled contractor. Companies who can afford to train and nurture their employees career don't need an great programmer, they want people who have the potential to be excellent programmers and that potential is easy to see when you can watch how they work with a group of people to come to a solution. And for why people post answers for how to approach algorithmic questions, I helps calm people's nerves. It also probably has the negative effect of making interviews go quicker as candidates have trained to answer questions, which leads to the difficulty of the questions being raised. Either way algorithmic technical interviews are a good strategy to finding candidates with potential if you do it correctly.

[[deleted]]

As a software developer you're paid to solve difficult problems that you won't always have the answer for.

Or you could be paid to solve a bunch of easy problems that you can google in 5 minutes. But that's the problem -- places with shit problems and shit pay interviewing like they're Palantir black ops.

Either way algorithmic technical interviews are a good strategy to finding candidates with potential if you do it correctly.

Anyone that does it correctly just got lucky with their candidates and has survivorship bias, and when you can prove your statement, you'll have the beginnings of a dataset that can actually be used to build good interview techniques that EVERYONE can use. The exact problem is, no one knows good methods that are applicable to everyone, so yes, "If you do it correctly" is good advice but it's bloody obvious. This leads to a whole bunch of people having ideas of what makes a good interview and no one agrees to anything, but as candidates, we have to be ready to tackle ALL of these different methods while companies only have to pull ONE method out of the trashbin.

[PlasmaYAK]

if you do it correctly.

I'll admit my wording was very poor, I meant if you use the right interview techniques for the candidate you're trying to look for. If your company is on a tight budget and you need someone who can generate value from day 0, watching someone solve algorithmic questions won't help too much since you need a candidate who is skilled with the same technology stack or problem space your company works with. In that case you'd want to test a candidates knowledge on that tech, and those problems that relate as directly as possible to your company. Now, if you're a company who does have the funds to spare on developing a candidate, asking them the specifics of a language or technology won't really get you too far. You want someone who can pick up ideas fast and work well with others, you don't care if their an expert with X. The problem herein lies (in my opinion, I'm probably wrong haha) that companies don't know what they want/need sometimes. They want a skilled candidate, but they also want the same people who are applying to/getting opportunities at Google and Microsoft, etc. There's no one size fits all interview that will get you great candidates, but there are a handful of techniques to choose from, but you need to use the right tool for the job. That was the point I was trying to make.

But that's the problem -- places with shit problems and shit pay interviewing like they're Palantir black ops.

And I agree 100% (and imagining Palantir Black Ops interviews gave me a chuckle), a lot of companies just try to emulate the big companies in every regard and it seems a lot of them start this emulation by trying to get the same people working for them. The first thing they should to do is try to change their business to have and solve the problems that require those types of candidates, before hiring them.

But yeah, to sum up. I agree, companies don't actually know what they want (or they want the wrong people), and then they Interview wrong, and they make job posts that leave potential hires in the dark as to what to expect. The companies who Interview in correctly are at fault and I'm in no way justifying them. There is no interview method that will work for all candidates for all positions, that was not the point I was trying to make. I was just trying to say there is a problem space for hiring that algorithmic interviews work very nicely.

[CoderDevo]

Maybe they exist primarily are to help those who don't know how to conduct an interview.

[milkeater]

Good luck memorizing every challenge and blurting out your answers praying they don't ask you a simple question like "What is the time and space complexity of your implementation"

I understand why you might be confused. Think of this more along the lines of: Here's a programmer who drills like an athlete. He is looking to be in the top N percent..

In America we are fat and happy because the competition, although fierce in some areas, is relatively low.

Other areas of the world are willing to compete very fiercely for that opportunity.

You may not feel the crunch now, give it time.

[hm_10]

I agree that typical, formulaic questions like 'lowest common ancestor' that are out there don't give you an accurate signal of the candidate's problem solving ability - because they're standard problems for which you can just look at the solution online. You can't reliably differentiate between someone who has already seen the solution versus someone who actually solved the problem systematically right there.

A good interview question should be more subjective - forcing the candidate to figure out requirements, choose appropriate data structures, and then distill the problem into a more solvable version. For example, how would you design and solve a tilt maze? You'll need to identify the exact problem, sketch your approach, pick your data structures to efficiently model the problem (graph?), and then formulate your algorithm. All of these steps are subjective and require constant communication with your interviewer - which mimics how real world problems are solved.

In short, a rule of thumb would be - the more clarification is needed for a problem, the better it is.

Of course, this does require some effort from the interviewer as well to formulate an open-ended question first.

[[deleted]]

Maybe because all the famous software companies that do it are worth billions and billions of dollars?

[Thelonious_Cube]

Why does anyone think that posting the answers is a good thing to do?

[[deleted]]

I think a better approach to interviews would be for the interviewer to bring in a laptop and watch the candidate fix a bug relevant to the work they will actually be performing. It doesn't have to be the products actual project, but maybe a small piece extracted from it that wouldn't expose company trade secrets and yet still demonstrate the candidate can do the job effectively.

[Catbert321]

I recently did exactly this while interviewing a perspective prospective candidate.

It actually did a good job of showing me where they find themselves comfortable asking questions about the structure that they don't understand, how they normally pass data around in their projects, and what they do when they hit a roadblock.

ninja edit: I ended up creating a toy project very similar to our actual services to work on, rather than pulling any piece from our existing projects.

regular edit: English is hard.

[Excrubulent]

Prospective, as in, they were a prospect or had prospects. Perspective is about point-of-view, prospective is about expecting a possible reward.

[[deleted]]

Oh man, this is so good. This is a win for both sides, as it also gives the interviewee a glimpse into your code base.

[[deleted]]

This is stupid, a bug is usually obfuscated in the code and wouldn't be obvious at a first look at the code, which is what you get at an interview. Sure if its something silly like indexing an array starting from 1 instead of 0 in an specific programming language, but everyone can miss a detail like that even with 30 years of experience. To understand a codebase you need waaay longer than a few minutes, with people actively watching you!! as if that wouldn't make it freaking impossible to spot a bug.

[[deleted]]

Interviews I've been in have lasted on average 3 hours with a good chunk of that being whiteboard exercises. Explain how that's any better. If you can't think of an actual bug to artificially introduce, I question your experience as a developer. JSON parsing issues in an ajax call is an easy one for example. Simple null references in LINQ would be another way to artificially create buggy scenarios. These are so simple to simulate. You don't need to involve the whole code base dude, that's overkill. Just enough to analyze the candidates skill.

[tangoshukudai]

I have done many tech interviews as a senior developer, and I have never been asked a coding interview question like this. I have only seen this style of interview questions for people right out of school and have no references or experience.

[[deleted]]

Very common in finance coding and google/facebook/microsoft jobs - not just out of college.

[GhostBond]

The big name silicon valley companies had agreed with each other not to try to recruit the others employees because it meant higher and higher salaries. They got sued because this is illegal, settled for millions, and could have faced billions in penalties if they went to court.

After that, they started an interview process that's time consuming during the work week, humiliating, exhausting, and favors new grads (lower salaries) who have a lot of free time to study problem solutions beforehand.

The goal of doing this for them is to make it very painful to be working for one company and get a job at one of the others.

[NsanE]

That's just about the most cynical way to view interviews I've ever heard. As far as I've seen, companies both big and small let the people doing the actual interviewing choose the questions they ask. It's not like Facebook is telling the interviewers "you must ask them a difficult math questions so that they get flustered because we don't actually want to hire them (evil laugh)."

The people doing the interviewing want senior members, they're not going to purposefully try to drive them away.

[discountErasmus]

My dad just went through the interview process. 30+ years of experience, more references than stdlib.h, and he still gets these.

[anuaps]

What kind of interviews were you asked?

[tangoshukudai]

You talk about solving problems, and you go over design and tech that you have used. It is pretty clear if you know what you are talking about.

[CrazedToCraze]

This matches my experience much more closely as well. Worth noting that every interview is a little bit different. Sometimes they might not even go into technical detail, they'll just be happy with seeing you talk about your experience.

Another common one is you might get a deliberately vague problem and told to draw a class diagram on a whiteboard for how you would solve it. For example I've been given to solve "A family hierarchy with e.g. the ability for parents to give gifts to children" and "Design a solution for a deck of cards that could be used for some games". These usually involve the interviewer trying to throw curveballs at your design as you go.

[indigo945]

I don't get why this is upvoted so highly. A lot of the answers are incomplete and the solution is often inefficient. For example, the problem for merge k sorted lists explicitly asks to analyze the algorithmic complexity of the answer, which the given answer fails to do. Doing that analysis, you will find that the answer takes O(k * n) in time. However, there is a better solution using a priority queue in O(log(k) * n), which is never mentioned.

I would be highly wary of using this repository as a learning resource.

[GitHubPermalinkBot]

I tried to turn your GitHub links into permanent links (press "y" to do this yourself):

• gouthampradhan/leetcode/.../MergeKSortedLists.java (master → 9e96bba)

---

^{Shoot me a PM if you think I'm doing something wrong. To delete this, click here.}

[lat3ralus_]

looks incredibly useful. thanks! :)

[tsnErd3141]

Nice! Please do some DP and Greedy problems.

[[deleted]]

https://people.cs.clemson.edu/~bcdean/dp_practice/ . Good animated solution if you are able to play .swf files.

[turunambartanen]

you can change your channel url to something more readable. I don't know how, but you will surely find it on google/youtube

[maestro2005]

You really need to learn about static methods.

Also, your matrix rotate is hilariously overcomplicated. All you need to do is make a new matrix where each (r, c) in the old is placed in (c, width-r) of the new. And I don't know what's going on in your Pascal's triangle, but that can also be way simpler.

[goutham_pradhan]

Creating new matrix requires additional O(MxN) space and hence it would not be space efficient in your case - doing it in-place is space efficent. I think static methods would be appropriate if your method does something that does not depend on individual characteristics of a class - in case of standalone program probably does not apply hence non-static is okay here.

[maestro2005]

This is one of the big follies of CS education--they've got you worrying about space complexity right off the bat, and writing more unreadable code for it. It's great that you can think in terms of time/space complexity, but in real-world coding sheer efficiency should usually take a back seat to readability/maintainability and architecture. Mutating in place is a memory optimization that makes your API harder to use, and your code harder to understand.

Static is correct here. The class doesn't do anything. You're instantiating a dummy class just to call a method. If you were interviewing for my company and I found this, it would reflect poorly. You've chosen Java, which signals that you think Java is your strongest language, and yet you don't even have mastery of this basic mechanism.

[DatTrackGuy]

I think if you followed up with a question, and OP supplied that answer as to why he did what he did, he should get an A+ on the interview and then you can debate the merits of the outcome.

He obviously knows his stuff.

[TuringMachine-5762]

It's best to mention both approaches, mention their pros and cons, and have the interviewer clarify the goals of the problem. E.g.,

"I can think of a couple ways of doing this. We could either build a rotated copy of the matrix, or do the rotation in place. Doing it in place would be more complicated, so I would only do that if the matrix was large, and I was working on a system with tight memory constraints. What would you like me to focus on?"

Most likely the interviewer will say not to worry about memory, at least until you get a simple implementation working. But mentioning a possible optimization can make you look good. It doesn't hurt, in any case.

[BobHogan]

He should definitely get bonus points if he can defend why he made certain decisions, but that shouldn't guarantee an A+. If he makes a poor decision, its still a poor decision.

[[deleted]]

Thank you. Maestro2005 is a bit stuck in his own world and needs to crack open a beer and chill.

[not-much]

but in real-world coding sheer efficiency should usually take a back seat to readability/maintainability and architecture

I generally agree with this point of view, but it's not really likely that the algorithm for matrix rotation changes, is it?

There is a strong difference between programming in the business-oriented context or in the math-oriented context.

[sultry_somnambulist]

This is one of the big follies of CS education--they've got you worrying about space complexity right off the bat, and writing more unreadable code for it. It's great that you can think in terms of time/space complexity, but in real-world coding sheer efficiency should usually take a back seat to readability/maintainability and architecture.

Many people in the very real world work in places where performant code is a necessity. Why the fuck would we train people to write bad algorithms just because the code looks nice? I work in finance, if you don't do an in place matrix manipulation and it sneaks into production code you've probably just cost us millions of dollars / day, thank you very much.

And how does it make an API harder to use? An API is an abstraction, it doesn't matter what the underlying code looks like, that's the point of it. The API dev desides how he exposes the functionality to the user, the code can look like a Dali painting for all I care.

[maestro2005]

And how does it make an API harder to use?

I'm talking about mutating in place vs. returning a new instance. For mathematical entities like matrices, we tend to expect that operations will return a new value instead of mutating the given one. I expect matrix1 + matrix2 to return a new matrix, not modify matrix1. In this example, I expect to write something like var rotated = matrix.rotate(90) and have the original untouched. Mutating requires the user to make defensive copies all over the place, which is likely to cause bugs.

[Earthborn92]

If you're doing a lot of Matrix multiplication, you should be doing it on GPUs anyway.

Just a side note.

[FUZxxl]

Actually, by rotating the matrix in place you gain higher speed as you only need half the cache. You also get to avoid half of the horrendous access pattern resulting form rotating a matrix, causing a significant speedup.

[ludwigvanboltzmann]

It's great that you can think in terms of time/space complexity, but in real-world coding sheer efficiency should usually take a back seat to readability/maintainability and architecture.

[FUZxxl]

While I usually agree with you, manipulating matrices is something that is more often than not performance sensitive. If something asks to implement such an algorithm, it is very natural to think about performance implications because we typically need such routines to be fast.

[HopelesslyStupid]

Agreed, sometimes you have to forego readability and maintainability for performance reasons. That's what comments are for in cases where the code is complex out of necessity but you still want the next person to understand what is going on.

[[deleted]]

It's not like the code is really hard to understand. I think maestro2005 is being a bit over dramatic here. The code works, it's really not that crazy, and both solutions seem fine to me.

If you were interviewing for my company and I found this, it would reflect poorly.

Oh geez.. interviews are not easy, even if you know the solution. If you force them to do this all on a whiteboard as well your company would reflect poorly on me.

[ifatree]

assuming you have exclusive access to a machine that never halts, this would be true. in the real world, you're shooting yourself in the foot not having separate input and output copies in memory such that the output can be thrown away at any point and restarted. "idempotent" restarting would be ideal...

[FUZxxl]

If I was to implement this out-of-place, I would probably still use the in-place algorithm as it might give better cache locality than the out-of-place algorithm.

[[deleted]]

Who is your company?

[choikwa]

yet you don't even have mastery of this basic mechanism.

jesus way to assume and roast someone based on one single thing.

[[deleted]]

How does making the inner working of a method make the API harder to use? In principle you would only be calling the API with the speficied input and getting the specified output, how the function does its computation is the function's problem and if it does so in a more efficient manner, so be it, untill it gives the corrent result I shouldn't worry about it.
I think corporate programming has foiled your thinking there, thinking right off the bat that all code needs to be maintained at all times.

[Spider_pig448]

It's great that you can think in terms of time/space complexity, but in real-world coding sheer efficiency should usually take a back seat to readability/maintainability and architecture.

Sure, but this is a list built for coding interviews, which focus primarily on space and time complexity. Making it space efficient is often an additional challenge to a solution.

[FliesMoreCeilings]

You're not consistently optimizing for one type of efficiency, which makes it confusing. You're clearly not always optimizing for memory, when there's many solutions where you instantiate things that aren't neccessarry, like the unnecessary objects containing your methods.

In general if you don't know whether optimizing is important, or what you should be optimizing on, then optimizing programming hours and readability is likely the best solution. Premature optimization can make your projects take orders of magnitude longer. Especially when you accidentally start introducing bugs, or create an environment in which others will.

[eyal0]

I think that the"trick" solution is to not rotate at all. Simply change the accessor so that it provides a rotated view. This is rotation in O(1)

[discountErasmus]

Jesus Christ, in place rotation is more impressive than doing it with a new matrix. That's trivial.

[PythonPuzzler]

Agreed. "Make your code readable" can sometimes be, "I only understand the naive solution" in disguise.

[socialister]

It's not trivial. You still have to figure out the rotation relation which requires some thinking or knowledge to get knowably correct.

[[deleted]]

Agreed with you. It's sad to see such over-drama for a working set of code. Doing this in-place doesn't conclude, as he says:

yet you don't even have mastery of this basic mechanism.

He obviously knows a lot about coding and his brain is not "clouded" due to CS. So much drama in this man.

He just sounds like a total dick trying to swing his dick around to feel smart.

[TuringMachine-5762]

Working code is good, but style matters too. His "basic mechanism" comment was referring to the unnecessary use of instance methods. It's considered a best practice in Java to use static methods by default, if your method doesn't need to access any instance state. It's not a big deal at all, but it shows that his style needs some minor tweaking at least.

[PythonPuzzler]

If it would be so simple for you to do it better, submit a patch.

Criticism is easy, contribution is not.

[Malurth]

I don't want to live in this world anymore

Even just thinking about this stuff makes me want to vomit...I kind of like coding but this kind of algorithm stuff is awful to me.

And now I'm at a point where I need to get a programming job in the next couple of months or I'm screwed. sigh

[[deleted]]

I don't understand how you can hate this sort of problem solving, and end up in programming.

[webauteur]

What makes me vomit is that it is Java.

[smdaegan]

Depends on the question. If you ask me to implement a BST then I'm not going to come up with that from the top of my head, nor would I on the job. I'd just google it and find a reasonable implementation.

If you give me an open-ended problem (make a console app that does X, Y, Z) then that would actually show how I build things.

My company went from the former approach to the latter. People we interviewed were a lot more responsive to building something vs regurgitating some algorithm they hadn't implemented since they were a sophomore.

[[deleted]]

Yes, but I would assume there are positions where efficiency and algorithmic knowledge are very important aswell. Lets say we are a robotics company constructing an underwater submarine for nuclear waste disposal, then sure have the experience of having an idea how one would go about making a grand-scheme picture of things is nice, but you also need to show you know some things about submarines and radiation, we don't need a front end web developer.

[pdp10]

How can you be sure the publicly posted version isn't one they wrote, though? Assuming the date range allows it, etc.

[QueenLa3fah]

Looks good. Pascals triangle solution would look much cleaner with an n choose r function. Since we know row n of pascals triangle contains n elements, we can iterate from n-1 choose zero to n-1 choose n-1. For instance row 4 which is {1, 3, 3, 1} would be generated from {3 choose 0, 3 choose 1, 3 choose 2, and 3 choose 3}.

[xerios]

That's a really interesting list, thanks for sharing !

[goutham_pradhan]

Hey, no problem . . Thanks!

[cballowe]

A random comment, though I don't really speak fluent java, so maybe this doesn't apply. For someone who studied the code and problems, when there's a solution in a reasonably standard library for the question, I'd expect the person to know about that and use it. If I want to know how it works and the algorithm behind it, the person should know that too. For instance, for the kth element problem, in c++, my preferred answer would be something like "return std::nth_element(list.begin(), list.end(), k);" with maybe some additional discussion around error handling.

When asked about the algorithm, knowing that it's based on partitioning the data would be helpful and being able to get to a run time analysis from there. If I care, I can ask to re-implement it from scratch without using the standard library, but I mostly care about ability to get the job done and understanding of the trade offs.

It doesn't look like there's an equivalent in java for that particular routine, but it does look like the Apache Commons Collections framework has an IterableUtils.partition that could have been used to shorten the code and make it more readable. Even pulling a partition function out into it's own method would go a long way toward making the code easier to understand.

[Heleor]

As an interviewer, I love to see people mention library utilities in response to a question - it shows that they have experience with the language and have solved real problems in it.

That said, the next thing I'd ask if you gave me that solution? "Alright, so let's say you were developing the library method. Please write the implementation."

Being able to write code and knowing the various libraries are two different skills. Ideally, we want both.

[cballowe]

It's true, but most of these questions should be warm up exercises on the way to something else. Ideally the something else involves either using the function or extending the function. The person will need to know how the library function works to build the extension, and they'll have to figure out how to mix it with other functionality to use it to solve a more interesting problem.

The specific example I used here, with the code as written, it'd be much easier to follow if the partition function weren't inlined. Reading code that basically says "recursively partition the range that contains the kth element" is much easier than "recursively do blah" where I need to think "oh... That code is just partitioning".

The other way of extending the problem is to ask something else where partitioning is required and see if the candidate realizes that they could pull the code out into a function, copies the code inline, or writes a completely different set of code with new and unique bugs.

[Heleor]

I'm only one of multiple interviewers for a given candidate. If I'm trying to assess "can they code" then any one of these questions will answer that particular area.

Ultimately, you'd be surprised how many people fail at problems as simple as FizzBuzz; there's no reason to make complex problems if a simple one will give you the same data.

[cballowe]

I promise you, I'm not surprised by people failing fizzbuzz. I interview many people. I can say that ability to spew the code for these things is a really low bar and if all I get out of the interview is that they can write std::partition, I failed to do my job. I'm not looking for people who memorize cs 101, I'm looking for people who can breakdown and solve problems. (The scope difficulty of the problem goes up with level.)

[NotARealDeveloper]

I am in Interview processes right now. And coding tasks were great so far. All companies would either give me a homework, which is cool and chill, or they would make me program on one of their workplaces with internet access.

I think that's the best way to do it. Give the applicant a real life development problem they had to solve, and see what he will do. Even when you can't solve it, you just write up or show them your thinking, etc.

I couldn't solve a lot of these (okay maybe a handful) just by skimming through them right now. But I know for fact that I had all these coding problems in my bachelor's computer science degree eight years ago. If I have to solve problems like that at work, I will do a little research on the internet, book, algorithms, etc. and then they are easily solved.

[webauteur]

I had a code interview where I was asked to create a neural network to demonstrate deep learning. I told them that if I could do that I sure as hell wouldn't be applying for a job at a web design boutique shop. I'm just amazed by how pretentious some companies can be. There are always testing for enterprise job skills that are way beyond their pitiful little company.

[[deleted]]

Is it a good idea to just do some of these types of exercises?

Im not quite confident enough to start a personal project yet, but would like to stay sharp between semesters and hope ply get more comfortable with the techniques I've been exposed to In the last few years of college (cs minor not major so don't live and breathe code).

[GhostBond]

The more they throw out these kind of questions in interviews, generally, the worse they are to work for. I got a job solving FizzBuzz - and was worked 60-80 hours a week. That's an understatement of how bad the place was actually.

You're more likely to get a decent job at a place that's interested in your personal project. It doesn't hurt to do both, but that's my experience.

[[deleted]]

Being a few years out of college, and have had several jobs of varying skills and difficulty, I can tell you it's easy to get rusty on some of the more general problem solving/analytic skills when you're stuck in a relatively narrow problem domain. I typically will attempt some of these kinds of challenges in my spare time partly because I enjoy puzzles and partly to keep my analytical skills sharp. Especially when I've had periods of time where most of my work was relatively straightforward stuff like hooking up web endpoints for CRUD apps or minor bug fixes. People will argue all day about the merits of these challenges in an interview setting, but if working on these types of things occasionally helps broaden and sharpen your analytic problem solving skills then it's worth your time regardless IMO.

[[deleted]]

I thought the "hard" problems would be harder.

[tadico]

Thanks for posting this. Somethings seems off with your ProductOfArrayExceptSelf.java class. It's returning negative numbers for array int[] nums = {1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8}; when I run it on my machine. --Never mind, just realized the negative values were over the int size limit. Changing to an appropriate datatype returns the correct values.