A few reasons I like them:
1. The goal is to come up with a workable solution - not to try to fold your brain inside out to optimize them like leetcode. They feel a little more "real-world" (though still firmly in the domain of programming puzzle)
2. There is a community that all solve them at once. At my company, we have a leaderboard and a Slack channel discussing them every day. And then there is the Reddit and everything else that makes it feel more "fun"
3. They are bound (only 1 problem a day). Some days are longer, but I don't get overwhelmed like I do with leetcode where you can lose hours just churning through problems.
IMO, they are a fun community programming puzzle tradition. I would still turn to leetcode for interview practice. But AoC is awesome for me when I don't want to grind leetcode for some interview I don't want right now.
We do something similar at work. We have a Slack channel and a private leaderboard, but we also have prizes for getting a certain number of stars, and also do "challenges" like most unique languages or using an esolang for a day. We also had some non-software engineering people take part and they had fun too. Last year was the first year we did it and it was well received.
At least for me, it's like... infinitely more fun than leetcode. The problems are bite-sized enough that I can usually get something done in less than an hour (although usually there's at least a few in the mix that take a long time to finish). There's a lot of personality in the website and text of the events that add to the fun factor. I like how the problems are broken up into two phases and how the second phase often throws a wrench in my previous solution or forces me to learn some tricky thing to get by.
cute stories, whimiscal ascii art reveal over time, problems of various difficulty, and the cool (to me) idea that many people are working and "struggling" with the same idea/problem over time. I'm also in awe at the work that goes into it. It's like watching a master craftsman to consider Eric making 25 unique puzzles, testing them, crafting many inputs that all work with the same rules, writing hints and stories to go for each puzzle. It boggles the mind.
It's more whimsical. There's a clear end with less pressure and an excited community to discuss with. At least that's what it's like for me (though I do also enjoy leetcode occasionally to be fair)
I wonder if there is a more productive form of it that helps learn/practice difficult technologies in a short amount of time. Say a combo of Ray tracing in a weekend, a game with reinforcement learning etc that helps people learn disparate technologies that they may not be familiar with while staying grounded on practical yet difficult problems.
FWIW AoC is great and anything that keeps the core CS spirit going seems like a good thing!
Advent of Cyber is that for infosec. It covers a broad range of security topics but is designed primarily to teach the basics of each topic rather than to be a test of advanced skills.
When it was done in a private leaderboard in a traditional in-person team working in the same office it was a great watercooler talk topic and code-golf team building topic.
I tried to do it in a remote work team with weaker personal links, and it felt like a chore, so this year I'm not doing it at all. No fun without the in-person code reviews and pair-programming code golfing.
Also many of us tried new languages of paradigms every year.
I find nothing wrong with Leetcode. I've been avoiding it forever, and finally started to practice it 2 months ago. I can say I learned quite a lot. Thus far in carrier I've primarily relied on `List` when it comes to data structures, now I realize how wrong I was.
I'm only into it because I know other people who are into it and it's fun to talk to them about it. It's actually my least favorite kind of programming problem, and the christmas elves conceit is very irritating to me
