As someone who codes basically only when AoC is around, and can solve like 70-80% of the puzzles, I am constantly wondering if this skill would be enough to get a job in the industry. Obviously stuff like Git would still needed to be learned, but purely using AoC as a Benchmark of problem solving through using code, would that be enough?
If you have no other experience you can point to, I'd take one or two of last year's AoC puzzles you solved and write a short write-up on how you solved it. Explain the problem, explain why it's hard (it's a challenge after all), talk about failed attempts (this is important), and talk about how you solved it.
I'd include this with your resume or cover letter.
Remember, the goal is to get to the next stage of the interview process - so you want to give them something to signal you're worth interviewing. AoC (or open source work) gives the interviewer something to ask about.