I solved a few of their problems almost 10 years ago. Looking at my repo I have absolutely regressed mathematically. I apparently solved project 15 without any code: https://github.com/aleda145/projecteuler/blob/master/problem...
(spoilers for: https://projecteuler.net/problem=15)
No way I would have reached for combinatorics if I got this problem at work.
This makes me a bit sad :(