In the past, Spotify challenged job seekers with puzzles. It looks like they are no longer listed; however, the pages are archived at the Wayback Machine; links couresy of my friend, Matthew Davidson.
I plan to solve all of these puzzles using Java and/or C++. Details are in the individual puzzle's README.
Best Before - ACCEPTED
Difficulty: Reggae
Ticket Lottery - ACCEPTED
Difficulty: Funk
Bilateral Projects
Difficulty: Heavy metal
Reversed Binary - ACCEPTED
Difficulty: Reggae
Zipf's song - FUNCTIONAL
Difficulty: Funk
Cat vs. Dog
Difficulty: Heavy metal