The 2019 Advent of Code has started.

For software geeks, whatever your language(s) or level of ability, the annual Advent of Code puzzle challenge is a fun set of coding challenges (some challenges are quite hard, but there’s plenty for us non-experts to work on). Here’s how the “about” write-up summarizes it:

"Advent of Code is an Advent calendar of small programming puzzles for 
a variety of skill sets and skill levels that can be solved in any 
programming language you like. People use them as a speed contest, 
interview prep, company training, university coursework, practice 
problems, or to challenge each other.

You don't need a computer science background to participate - just a 
little programming knowledge and some problem solving skills will get 
you pretty far. Nor do you need a fancy computer; every problem has a 
solution that completes in at most 15 seconds on ten-year-old hardware."