Job interviews

Like it or not, technical interviews are still a reality in the software industry and I don’t expect this to radically change anytime soon.

Getting a job in a place where you have no connection can prove very hard. The obvious guess: the bigger/hotter the company, the harder. You may try to be original but I’m not sure this works very often for technical positions. From my experience, you better be concise, have a clear message, show why you care about the company you’re applying at and hopefully you’ll have a chance to show them your abilities. Of course, if you’ve already shown the world with some of your project, this might have proven easier than it sounds to get to the interview process.

A critique

Most of the time, recruitment processes just suck:

  • companies do not know exactly what role/competence they actually need making the process somewhat ‘fuzzy’.
  • companies delegate the early process to external recruitment agency whose interest is not really aligned with the company; they often don’t really understand the technical challenges and do not know the company culture well.
  • most job descriptions sound like companies are looking for people ready to master their role from day 1. What about learning? Does it mean the company just look to hire someone from a competitor (that likely have quite the same technological stack)?
  • either companies or recruitment agencies ask you to be available on office hours and for long times. This is plain wrong. Even if I’m willing to change job, it doesn’t mean that I’m not involved in my current position. Recruiting is one of the most important aspect of a company so it is your responsibility to adapt.
  • salary negotiation is a biased game where the interviewee is often being tricked. The company is not looking for your ‘real’ value but the lowest salary they can pay you. Neglecting the salary will often lower your motivation to perform at the job very soon. Do not lower your salary expectations and even better, do not reveal your expectations first.

Knowing this, job interviews are an exercise that requires a good preparation.

Screen interviews

The first step will probably be a phone call with some HR. Be prepared to explain your experience as briefly and clearly as possible and try to be passionate about what you’ve accomplished so far. In my experience, you have to be able to explain the logic out of your different experiences to show that you have not been changing jobs for the sake of it (or the pay) and to “justify” why you are actually having this interview.

You might then have a technical screen interview where you’ll be asked some questions such as:

  • explain the latest project you’ve been working on
  • do you code at home?
  • explain differences between a thread and a process
  • explain what a hash table is, what it is used for and how it is implemented
  • explain what a critical section is
  • explain what a deadlock is
  • sort a list of words
  • explain how the sorting algorithm works
  • sort 5 petabytes of words
  • reverse the words in a string of multiple words without using more memory than needed (e.g. “dog cat” should become “cat dog”)
  • count bits in a integer (write actual code via skype)
  • given a function to print one char, write a function printing a string without using iteration
  • count the number of single child in a binary tree
  • determine if an array of integers contains duplicates
  • do you have any questions?

Those are not difficult questions but still you have to be prepared as, if you do not regularly practice, you may have forgotten how Quicksort works. Also it is important that you know what you are looking for in your next job. This first step is both a technical and a ‘human’ filter and if you sound like you don’t know where you’re going with your carrier, you will likely not look attractive.

On site interviews

If you were convincing enough, you should go for an on site interview loop (and hopefully not the anti loop version). Here are some advice:

  • be prepared; you’ve heard it before but there is no secret. There is a part of luck and preparation. From my experience, you probably won’t have very very hard questions but still you need to have some practice.
  • stay concentrate; at big corporations, you may have 5 interviews in a row which can prove physical.
  • make sure you’ve understood the question; test your understanding with an example and ask your interviewer for validation.
  • smile and stay positive; there might be questions that you don’t know the answer directly. Do not show frustration. Show you are thinking, interact with your interviewer to try to find a solution.
  • communicate a lot; explain your reasoning loudly. Your interviewer is judging your reasoning as much as your ability to solve the problem. And if you’re going on a wrong direction, he/she might even give you an hint early.
  • do not try to be too smart. First find a working solution and if the interviewer wants a better one or prefers to skip the easy one, he/she will ask you to move on to the better solution. But looking for a “not naive” solution you may give the impression that you like complexity which is not good. At all.

Here are some questions you may encounter:

  • given a list of reference words, write a method to list all anagrams of an input word. How would you design a webservice providing anagrams of a word?
  • given a list of reference words and a string with all whitespace striped, how would you get the list of reference words contained in the string maximizing the number of characters being matched (e.g. if reference = ["the", "then", "nuke"] and string = "thenuke", you should return ["the", "nuke"]) (here is a solution)
  • given a matrix filled with 0’s and 1’s, we want to find the largest contiguous region of 1’s. Implement code solving this problem. What if you are authorized to modify the input matrix?
  • given a biased coin, provide a way to get unbiased output.
  • given an array of size n containing all numbers from 1 to n, we replace one element with another (meaning one element is duplicating and one element is missing). Find those two numbers. Could you find a solution using O(1) memory?
  • how would you sample p number out of an array of size n with uniform probability? (see Reservoir sampling)
  • given a dataset with two columns, first_name and last_name, find all rows where the fields have (probably) been swapped.
  • given a list of hotels with their GPS coordinates, write code to find hotels near a given coordinate. What is the complexity? Could you do better?
    • we now want to improve hotel search by name. We want to use some specific ‘fuzzy’ matching. How would you implement a solution with the following rules:
      1. case insensitive;
      2. replace accented characters with unaccented one;
      3. be tolerant with doubled letters i.e. “fuzzy” and “fuzy” should match.
  • revert the bits in an int.
  • given an integer array, write a method listing all combination with repetition of those intergers in order. (Note: we want all n^n combinations! The “in order” information is important. As I said, you should write an example: [0, 1, 2] => [ [0, 0, 0], [0, 0, 1], [0, 0, 2], [0, 1, 0], [0, 1, 1], [0, 1, 2], [0, 2, 0], ...]. You should see a pattern. This is a simple increment of numbers in base 3).

In the end

You may have or not an offer. You may try to negotiate your salary but I won’t be of any help on that. However, just some final remarks:

  • ask questions about working conditions and philosophy: working long hours or crunch mode might not be what you are looking for, people might work on their own when you feel good in a collaborative workplace etc.
  • do not take a negative response personally. First time you hear ‘no’ it might be difficult (you might like reading The Now Habit). Analyze what may have gone wrong to do a better job next time (remember that in the anti loop case you are not really the cause). You may ask some feedback about what you could have done better;
  • working with people requires trust. You should probably not want to work in a company where you don’t feel you can trust your manager or colleagues. This is a rule your interviewer should apply but you should do the same as an interviewee;
  • if the company forgot to give you an answer, send them an email. A company not taking the time to give you an answer (which often is a standard email) is just neglecting its most important mission so it is likely a company that you do not want to work for.