Clojurians Log v2

Is that significantly faster than using a transient vector with assoc! ?

No idea about using assoc! I did try a few things on the way to aset/aget but they were too slow. If you want to try it out, my code is here: https://github.com/pshapiro4broad/advent2020/blob/main/src/day23.clj

My solution for day 23 runs in abount 9s with int-arrays, 13s with transient vectors, 18s with vanilla vectors here. fwiw & hth: https://github.com/next-mad-hatter/adventofcode/blob/master/src/aoc_2020/day_23.clj (transients) & https://github.com/next-mad-hatter/adventofcode/blob/master/src/aoc_2020/day_23_inplace.clj (int-arrays)

fascinating. thanks for sharing!

I really struggled with day 7. I tried to solve it without recursion. Modeling the data into a structure that made sense to me was kinda hard but was nothing compared to coming up with the ugly, imperative code that did the actual computation 😛(inspired by the topological sorting algorithm; I used 2, or maybe 3, atoms). It's not public yet but I'll probably put it on gihub as soon as I get a little bit further. 1. Any of you come up with a pretty non-recursive solution? 2. The recursive solution feels much more natural to me, so I've also been wondering: why is recursion so frowned upon and more or less considered "inferior" to an iterative approach? I understand that in some cases it's hard to understand but in this case I really don't see any reason to avoid it.

AFAIK, the only non-recursive approach to topo sorting is to use a stack and do DFS, right? I have no clue how that would work in idiomatic Clojure. This is one of the top hits on Google, and it’s using recursion: http://hueypetersen.com/posts/2013/06/25/graph-traversal-with-clojure/ The examples here are also using recursion: https://github.com/life0fun/clojure-idiom/blob/master/graph.clj

Indeed, stack + dfs is how I did it and it's probably the most unidiomatic thing ever written 😂 thanks for the response and the links 🙂

If you have some priority queue implementation then topological sort can be written as rather simple "loop" (whether it is expressed recursively or not is another matter somewhat)

true, the pseudeocode on the Wikipedia article does just that

One should take advice from people who consider recursion inferior with massive grain of salt afaiac 😉 Fwiw, or mayby luckily, this (it being frowned upon) had never been my experience. Which isn't to say recursion is equally useful in every programming language -- not every language supports tco, and even less support unlimited recursion in general. But if one wants to avoid mutable state there's no way around it.

From what I've heard, this year's aoc was a bit easier than some previous entries. I think I spent most time on (and had most fun with) day 11, seeing how far I could speed it up. Second would probably be day 23, trying out and comparing different vector types. The part I enjoyed the least was probably the last part of day 20, was a bit too long for me. And day 15 I cheesed, didn't feel like doing it at all 🙂

Was that day 15 or 13? Because day 13 was a really hard one for me. And I agree day 20 part 2 was a lot of work. Most of the other days weren’t that bad. Overall it seemed easier to me than 2019, which I got about 1/2 way through, or 2018, which I also didn’t finish.

I skipped implementing day 15. For day 13 I had to dust off and look up some long forgotten math, but coding it wasn't that bad.

2020 is the first aoc year I took time to solve all problems (but not in december :)), only did a couple from 2018 before that, so cannot myself comment on difficulty compared to previous ones, only hearsay

of course, the difficulty is somewhat subject to variation depending on which building blocks of the solutions one is willing to take from libraries -- 2020's days 18 and 19 would have definitely been more work without instaparse 🙂

I don’t really know clojure, doing advent2020 was my first use of it so I didn’t know about instaparse, although I did look at it for day 18. I ended up doing something cheesy with regular expressions. I’m sure using a proper parser would’ve been cleaner.

Ah, similar story here :) Took aoc as opportunity to practice clojure, whenever people mentioned libraries here, put them on my to-check-out list..

I guess some would only consider implementing a complete parser to be proper solution.. But that's the nice thing about aoc, only you get to set your goals and constraints :)