Can coders code?
When I was looking for a simple programming task that I can use to evaluate candidates, I had the following criteria in mind:
- solvable within 10 min
- does not require obscure algorithmic knowledge
- has potential for further discussion
- not language specific
I went through my list of simple problems (I only considered the easy ones) and I stumbled across Pairs. I instantly realized, that it is the perfect question. There is a brute force solution, the specification can be expanded, we can talk about sorting, hashing, hash collisions, Big-O notation and cases when the input does not fit in memory. Even Bloom Filters are a viable topic of discussion.
My first interview was planned and I was thrilled. I would use the challenge and it would be great! The first three candidates I exposed to the task failed horribly. They could not implement the brute force solution O(n^2) without bugs in the code. I was horrified. Is the industry really this bad? Can programmers really not program?
In the last 3 years I used this little coding task in almost 50 interviews and the failure rate is alarming. Only two people managed to solve it flawlessly. They both accepted the offer and I have been thrilled to work with them ever since. There have been others that got stuck in the weeds but nevertheless showed an ability to think. Kudos to those! I will expand on the definition of flawlessly below.
I adjust the -pass- criteria accordingly to the person’s experience (people who graduated a long time ago might not remember what Big-O is), title (did they code in the last job?), future job duties (are they supposed to code?) and the prowess with which they claim that they know how to program. Support engineers that have had limited exposure to python and shell are fine with something that resembles code. People that have been in the industry for a decade better be ready to go through at least 3 iterations of increasing complexity.
Before reading on, I suggest that you go and solve that challenge. I will wait….
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