What I Learned From Bombing An Amazon Coding Assessment

Andrew on August 18, 2019

Recently, I was invited to take an online coding assessment with Amazon. As I'm contracted with my current job for a while yet, I thought it might ... [Read Full]
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What I learned: a love for regex. I bombed, and I knew it. So I dwelled on it, and pretty quickly realized the proper solution was regex. Looked into it a bit, flash-forward years and years, and now I'm that guy who has a one-liner for every text-based thing ever lol.

There's real value in failing.
Frankly, I'm just as happy if I win or fail.


I've always wondered why they are called "regular expressions".. when in fact, their more like "special-ability-superhuman expressions". hahaha. Jokes aside, I've often decided to learn regex properly, but then somehow I never get past the 0-9 a-b... :D

On a sidenote, if your code is riddled with regex (highly optimised and beautiful) does it not make it more difficult for less experienced devs to make changes to your code? I guess I am asking if we should weigh up using regex, versus simpler string manips?


I think you can always help with understanding of regex by commenting and naming, just like you would with other code items.

  # number or plus as first character, number or certain characters as other characters
  BASIC_PHONE_REGEX = "^[0-9\+(][0-9)(\-\.ext\s]+"

Yep, very good. Perhaps even add the expected result as part of the comment.

When tdd is viable, rex can be expressed very thoroughly in tests. They need to be tested differently anyway because of their versatility, so those tests go a long way to show what it should/not do

regex101.com/ is a godsend when it comes to understanding someone else's line noise.


Yeah, sometimes it just makes sense to use regex, especially when looking for patterns in text. It's easier to say "look for \([0-9]{3}\) [0-9]{3}\-?[0-9]{4}" than:

  1. look for a ( character, if you find one, check that
  2. the next character matches any of 0, 1, 2, ...
  3. the next character matches any of 0, 1, 2, ...
  4. the next character matches any of 0, 1, 2, ...
  5. the next character is a ) character...
  6. ...
  7. ...
  8. ...

Rex is a little like awk. Despite my love for it, I use it in code judiciously - just for the sake of who-comes-next. If the thing can be done effectively otherwise, I'll probably use the otherwise. ...to a point. I'm not going to trade a rex for an On6 for the sake of who-comes-next lol.

For my own uses, though? Wait.. that form was misconfigured and now you have 840 contest submission emails you're manually copying/pasting to a spreadsheet?!?! Fwd those and give me 4 minutes. 🤓

:D hahaha. Seeing a good regex in action is literally like magic! Aloha-regex and BANG - magic.


+1 for regex. I still remember reading in the pragmatic programmer: "Pragmatic programmers master regular expressions."

Eventually I took a 30 day vow to do absolutely no text manipulation with anything but Regex. Now I, too can't put them down. I use regex for almost everything trxt parsing related. (everything except html, xml and JSON of course.)


I bombed an interview at a huge company because I didn't read the question properly! It was a true/false question that was worth like 15% and I just read the keywords and clicked true because I wanted to have more time for the coding problems.

Lesson learned: Triple read each question 😆


I nailed an interview once because I didn't process the question correctly lol.

Me: goes on a 7-minute spiel.
Interviewer: ... ... Well, that's not at all what we were asking. ... ... But tell me more about that.



Lol that sounds like something that could happen to me as well 😂


I would like to emphasize, that these kind of assessments only take a snapshot of your current development and problem-solving skills. A more valid approach also requires to monitor how your skills improve over time.

In the long run you want to hire someone who is good in self-improvement of skills and adapting to changes. Ans maybe this person has just not build the skills yet.

Failing this limited small puzzle makes me think in the end:

a) I just not solved it yet but in the future I would be able to do so


b) This would not be the place where I like to work at because the only thing they care is my current performance and not the performance I could deliver after x time-units of further improvement.

Hope this is not perceived as rude but rather a critical approach on code assessments we all should be aware of (and communicate in job interviews, too).

Still much thanks for sharing the test, it was fun to solve it <3


not even a snapshot of your current skills but those that you can think of immediately under pressure. Any company that wants someone who can solve puzzles is a bad company, I want to work somewhere where real engineering solutions to problems are considered, analysed and thoughfully developed. Not stupid puzzles.


I see the biggest conflict in long term creating quality software vs. short term KPI, where one qualitative measure is compared with a quantitative measure.

And HR, as well as MGMT, are totally in love with quantitative measures, which is why (I assume) they still do these coding or fact-based-recall-skills assessments.


Woof. I applaud the positive message in this post and I'm all for encouraging and helping fellow devs with information like this. But it missed the biggest lesson from the experience:

Memorization and regurgitation does not a good developer make. And we need to stop accepting it as part of the hiring practice.

Knowing where and how to find an answer, and how to apply it, is infinitely more valuable today. Hiring in tech is fundamentally broken.


I wonder if you are allowed to use your own code editor? I can imagine them tracking your typing/editing, and if you are just copy-pasting a solution into the editor at the end, then they might get suspicious that you have not actually programmed it yourself.


For the one I did, at least, they warned you that they would be recording your screen. So they could see everything I was doing, including googling and going to StackOverflow!


note to self: close pornhub tabs before starting interview. :-)


Know Big(O) notation, too. I failed with the questions and then they asked this as well. I messed up this as well so I'm probably from redoing it for life :-)


I love solving such problems on Hackerrank. They are not timed but they do run against several test cases. So it gives you practice to code against all the edge cases.


Great tips for interview prep Andrew. Thanks for linking to Coderbyte!


My pleasure! Was there a little bump in traffic?


I made the same like a week ago: having a kid around doesn't help. Request for silence with a few days in advance. Of course I didn't get it


Another comment for #4: the debugger can be a huge time saver!

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