A regex crossword from LinkedIn Engineering | Hacker News Reader

A regex crossword from LinkedIn Engineering

engineering.linkedin.com

66 pointsneilpomerleau40 comments

OP has posted this link before, both here https://news.ycombinator.com/item?id=10990206 (with the title "Get an interview at LinkedIn by solving this puzzle") and on the Who's Hiring threads https://news.ycombinator.com/item?id=11014173

As an exercise, I wrote a quick and dirty python script to solve this back in February (albeit it's not the most elegant solution but far better than brute force) and submitted my answer and subsequent contact info hoping to eventually hear back about said interview, and never did.

Which is quite frustrating from the perspective of someone on the job hunt. Why use something like this as a hiring tool and not follow up on it?

</rant>

This seems to be a common pattern. I suspect there could be a business opportunity here for someone to outsource intermediated job applications and keep track of both applicant and employer communications.

Plenty of sites try to match up the two sides but it seems most fall down at the point of initial contact.

I completed it too just for fun. I never was contacted either. At the very least, an email saying 'congrats' would have been nice.

Is LinkedIn a desired place to work? I've never heard anyone clamoring to work there.

Are you in the Bay Area? In my circles they are known as a good place to work.

That said, I don't understand why they've hired so aggressively nor what all those employees do, but they have a nice campus, good pay, and good perks.

I work at LinkedIn. Let me be the first one to tell you that it is an amazing place to work at! Everyone is super smart and talented. The infra teams have some really amazing projects under their belt - a lot of which are open sourced. I work on the applications team and I love the culture in our org - everyone is super friendly, helpful and it's a privilege to be working on products that are used by hundreds of millions of people and being able to call shots on them. Also as a relatively inexperienced dev, I'm given ample responsibilities to drive my projects and mould them that I feel are helping me grow. The perks are absolutely amazing - pretty comparable to the ones you get at FB/Google. My favorite ones are $2k reimbursement for fitness related expenses per year, an entire week off during Independence day and Christmas, a day off to yourself and your team each month (search for InDays), and frequent company and team outings (there was a screening for the last Star Wars movie and is another one for Batman vs Superman soon). I'll probably never work for another big company again after this for an entirely different set of reasons, but I am absolutely glad about my decision to join LinkedIn.

> not the most elegant solution but far better than brute force

Actually, brute force works just fine for such a small matrix:

https://gist.github.com/aexaey/3657fa39cc35c861f6d6

If you enjoyed that, there's plenty more where that came from at https://regexcrossword.com/

The linked in one was so easy that I felt compelled to play some harder ones - you definitely cost me a couple hours of productivity today - I've played through a couple dozen of these things...

So, thanks, and also no thanks ;)

LinkedIn thought, "We have a problem, not enough good devs." Then they thought, "Hey, let's recruit using a regex puzzle!" Now they have two problems. (With apologies to jwz.)

Point/joke taken, but let me play devil's advocate: anyone very familiar with regular expressions probably has a lot of experience as a developer. Is s/he a good developer? That's harder to say. But s/he definitely does have some passion for solving puzzles, at least.

I'd even argue that LinkedIn doesn't really even need amazing developers. As far as code goes, they're only really solving problems that have been solved for decades. Infrastructure is another matter, but I doubt they're doing anything insane on that front either.

This is typical of the same crap I see on my linkedIn feed. Solve this if you are a "GENIUS"!!!! popsicle + popsicle = 6 toilet * toilet = 9 popsicle + toilet =???!?!??

I have made heavy use of the block feature. And to those of you thinking of answering those, its a lose-lose proposition, you either get it wrong and look ignorant, or you get it right and look like a slacker...

Obviously 0 or 2/147. ^^

Only 12% of people who attempt this puzzle solve it.

Static text or real statistics?

I received the same stat.

Same here. It's probably a hard coded message. You'd think the hacker news post would skew it a bit if it was realtime. Either that or they have a really massive data set on it that's hard to skew.

That "solved" content is loaded from "static-sites" location [1], so most certainly hard-coded.

[1] (spoiler alert, do not read the slug of this URL) https://engineering.linkedin.com/content/dam/static-sites/en...

Solved this puzzle last time and LinkedIn basically told me "we won't actually interview you unless you have 2-4 years of industry experience" new grads be warned.

I really don't understand what the point of creating these puzzles and then failing to disclose that you'll reject, out-of-hand, an entire subset based on such hidden criteria. It feels like firms want anyone else, but themselves to train junior|entry-level|new grads or only accept new grads with the requisite level of moxie who have had the luxury of time and money to have trained themselves or been able to establish businesses.

Some people had to work whatever job(s) they could find or had family issues to deal with and go to school at the same time. Are they less qualified because of it?

</rant>

I solved it! They reached out about a day later (edit: and asked for a copy of my resume) and showed me a couple of job listings I'd be a good fit for. They wanted me to relocate which was kind of a buzzkill, but it was fun getting to talk with one of their engineers about how they've set up most of their projects. They were super nice, but it does take a while to hear back from them.

To up the ante, it would be a fairly good challenge to write a computer program that solves this puzzle efficiently.

Another commenter mentioned having written a program that solves it (though not necessarily efficiently).

I think that's what distinguishes the truly excellent/"lazy" coders from the head-down, 9-to-5 types.

This seems like a twisted idea of a "fun" interview question that "our candidates really enjoy"

if i had gotten this puzzle in a job interview i would certainly enjoy it but ymmv

Can anyone explain what the solution is supposed to look like? What actually goes in the boxes?

You fill the characters that would be matched by the regular expression given. So the character has to match both the row/column expressions at the position where they intersect.

Oh I gotcha. That makes more sense; I was confused since most of the expressions match more than 4 characters. Thanks!

The solution is a 4x4 grid of letters where each row and column match the corresponding regexes.

So the 4 letters descending from the column marked (LN|K|D)* should match the regex ^.(LN|K|D)*$ entirely. Hope that helps.

This was a cool problem. What would be even more interesting is generating puzzles like these.

Usually crossword answers make sense. This ended up just looking like a jumble of letters.

The jumble of letters made sense in the context of the regex problems.

The first regex crossword I ever saw — https://gregable.com/p/regexp-puzzle.html — also was sort of a jumble of letters, but it actually encoded a secret message (I don’t want to say more — spoilers)

I enjoyed doing this but I got a sore neck from reading diagonal text!

only 12% of people got this puzzle it says. I used rubular.com though, so maybe that was cheating...

What I got out of this: regex precedence rules are really unintuitive to me.

What is a precedence rule in regex? You can either derive a string or you can't. Precedence problems result in ambiguity, there shouldn't be any ambiguity here

The regex operators can be ordered by precedence. The whole point is of course to avoid ambiguity...?

It was fun but pointless. I would have been more impressed if the solutions were unique and dictionary words rather than trying to make silly regexs like 'not working'. Is LinkedIn even hiring with their current stock plummet and rumors of layoffs?

This was fun, thanks! Solved it in about 10 minutes.

I barely have any experience with Regex and it was not too hard to complete! I feel that it certainly could have been more difficult.

Reply on news.ycombinator.com