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.
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!
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.
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.
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!
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.
That's unfortunate, but logically inescapable.
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.
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.
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.
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"?
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 */
}
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.
usize len = strlen(foo);
char* bar = malloc(len);
for (int i = 0; i < len; i++) {
bar[i] = foo[len - (i + 1)];
}
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.
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).
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.
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.
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.
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.