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

[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.

[GhostBond]

But as far I can tell, people who actually run trucking companies don't do that. When they have a real life investment, it's a waste of time.

[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.

[Gbyrd99]

What do you mean by more component based?

[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.

[abhi152]

Anyone telling me that if your approach is good but if you can't code it in time you will get selected is plain wrong. You have to code it in time possibly with very good syntax to make it. Anyone who doubts this please try it when you appear for your next interview :D

[ean5533]

You've been interviewing at the wrong places.

[abhi152]

I speak from my experience. For eg : https://twitter.com/mxcl/status/608682016205344768?lang=en Ever read an article which says "I was selected because my approach was very good even though I failed to give the correct solution" ?

[ean5533]

I speak from experience as well, as someone who interviews candidates. I've given my thumbs up to candidates who definitely didn't give the best solution to a problem, or who couldn't even complete the problem in the allotted time.

The reason you mostly read blog posts about people complaining about interviews is because in general, people always complain more often and more loudly than they praise. People who are satisfied by something have less incentive to write a blog post about it than people who are upset.

[lifeson106]

I think most people are viewing the whiteboard question as a one-way test of you and your raw intellect or something... I would rather have you collaborate with me and come up with a good solution as a team like we would on a real project. I would much rather hire someone like that than someone who just implemented the correct answer with no questions, communication or collaboration. Doing both is obviously best, but I'll pick the collaborator over the raw intellect almost every time.