Advent of Code 2019

https://adventofcode.com/2019

by scottdw • 7 years ago

552 122 7 years ago

adventofcode.com

dang2• 7 years ago

Already discussed at https://news.ycombinator.com/item?id=21660423, but since it starts today we'll give it another go.

GaryNumanVevo• 7 years ago

oh lord, I just started writing a GCODE motion planner, I forgot about AoC.

evenh• 7 years ago

An alternative with daily articles across a range of topics: https://news.ycombinator.com/item?id=21675200

Barrin92• 7 years ago

Always enjoy doing these but there was one last year that nearly broke me. I think it was day15. It was the worst combination of mind-numbing coding and horribly hard to debug special cases. It was purely convoluted with very little to think about which makes for the worst kind of puzzles

m1kal• 7 years ago

Day 15 took me about 8 months, but I finally discovered I had made one wrong assumption that corrupted my solution for special cases...

cjauvin• 7 years ago

I can totally relate about that particular one, I remember that it destroyed a good part of a weekend for me, and I wrote that about it on Twitter, back in January of this year:

"I have thought about the particular challenges of this year's Advent of Code (which I greatly enjoyed once again, with some intermittent mixed feelings), and my conclusion is that some problems might very well be of similar difficulty levels, but with nevertheless very dissimilar frustration-inducing levels. And I think the frustration level is strongly correlated with the feedback signal one can use to debug. Case in point: Day 15, which was almost impossible to debug, once you had a working solution, versus Day 17, which was actually fun to debug, since the visual signal you could use was so strong."

AdeptusAquinas2• 7 years ago

That one wiped me out for a week too, and caused borderline psychological problems.

Ultimately though I realised that if I followed the description word by word, and made no assumptions, then I got the right solution. Still, a nightmare: you could pass all the examples, or even some alternate real sample data, and still get it wrong if you got the ordering slightly incorrect.

loeg4• 7 years ago

Yeah, it's really frustrating when the text summary is vague and underspecified. It makes it hard to understand exactly the result the author is looking for, which isn't the fun kind of puzzle.

wycy• 7 years ago

Day 15 was terrible for me too. The edge condition I missed was that you could both move and attack in a single turn. It only changed the outcome for me in part 2. I was only able to finally debug it by comparing debug outputs every step with a known-good solution.

m000• 7 years ago

I strongly disliked the puzzles that quickly devolved to correctly handling a ton of corner cases. 15 and 17 were both in this category. What's the fun in that? This is like the boring part of being a developer. Without the payment that goes with being a developer.

mathw3• 7 years ago

I hit day 15 and stopped last year. There always seems to be one puzzle which is so irritating it no longer seems worthwhile when I could be playing some music or building something in Minecraft or just lazing around on the sofa with the cat.

forrestthewoods• 7 years ago

Last year was my first year and I loved every second of it.

I strongly recommend using AoC as a tool to help learn a new language. Many people, myself included, use it to learn Rust.

The best part about AoC is the community. Everyone is super helpful and kind. The daily Reddit thread has solutions in every language under the sun.

My better half is a designer and is going to participate this year to help learn JavaScript.

donatj• 7 years ago

I always have a ton of fun with these sorts of things. I always wonder how they come up with these sorts of puzzles. That's not a skill I have.

dazwah• 7 years ago

There's a great talk by Eric Wastl that describes how he does it: https://www.youtube.com/watch?v=bS9882S0ZHs

dross• 7 years ago

This is my first year. As I missed the start time I created an event to remind me and published it for anyone else who'd wish to subscribe. https://calendar.google.com/event?action=TEMPLATE&tmeid=M203...

Looking forward to the fun, the stress and the eventual euphoria.

WrtCdEvrydy• 7 years ago

Could not find the requested event...

devit• 7 years ago

One line bash solutions: https://pastebin.com/QnKJEXxt

threatofrain• 7 years ago

Surprisingly readable.

noname120• 7 years ago

You can do shorter in languages with functional constructs. For example Python:

  sum(map(lambda x: x // 3 - 2, numbers))

skinnyasianboi• 7 years ago

Kotlin:

numbers.sumBy { it / 3 - 2 }

the-dude2• 7 years ago

Why is that a double slash?

empath752• 7 years ago

one line ruby map reduce:

    input.map(&(-> (f) {->(g) {g.(g)}.(->(g) { f.(->(*args) {g.(g).(*args)})})}.(->(f) { ->(n) { n < 9 ? 0 : (n/3-2)+f.(n/3-2) } }))).reduce(&:+)

nabraham2• 7 years ago

Eric, the author, says he won't accept any puzzle submissions because of attribution and legal issues. This seems like the wrong outcome for people who want to make the site better but don't want credit, compensation, or attribution.

Has anyone seen a site using an IP assignment agreement which is the equivalent of "take my work, I don't want credit, and it's just for your site"?

The Creative Commons CC0 license comes closest, but one could scrape those puzzles and create a competing site, which I'd guess Eric wants to avoid.

arve0• 7 years ago

The problem is trusting the submitter. How do you make sure derivate work is not submitted?

tl• 7 years ago

It’s a preference in his case that cannot be solved with licensing. Eric doesn’t want even potential ideas to influence him, and he says he has more puzzle ideas than time to implement them.

Personally, I suspect that he wants something that consumes so much of his free time to wholly be his, and I respect that.

inerte• 7 years ago

“your site” is really complicated. Who is “you”, person, website or the company? If it’s the person can they transfer the rights? What happens if they die? If they donate the estate? If they get hired or contracted? If the website expands scope or changes in any way?

nabraham2• 7 years ago

"You" would be the company, and the submitter would assign all the rights to it. Interestingly, I looked and couldn't find any terms of service or company name.

mjtlittle• 7 years ago

Maybe he enjoys/benefits from the work, I feel like coming up with puzzle ideas would be somewhat fun/beneficial. I would definitely assume that if this were not the case he would outsource it or maybe even open source it.

ahaferburg2• 7 years ago

If you want to help, why not ask the people running the site what you can do to help? Do you actually want to help, or do you want to make puzzles? Or do you just want to discuss a perceived problem that may or may not exist?

aquova• 7 years ago

Many of the comments are about the event as a whole, but I'd like to commend the author for the day 1 puzzle, which I think is very cleverly written. Many people (including myself) use these as an opportunity to try out learning a new language, and the first puzzle does a good job of making sure you know enough basic operations for some of the puzzles coming up. The puzzle itself wasn't very difficult, you could do it by hand if you really wanted to, but it required you to know how to read and parse lines in a file, handle compound data structures, iterate through, and perform basic operations (floor, casting strings to ints, etc). I thought it was really well done, and creates the basic knowledge for the puzzles ahead.

klemenk• 7 years ago

You can watch authors talk about how he prepares challenges and other challenges he had with AoC :D https://www.youtube.com/watch?v=gibVyxpi-qA&feature=emb_titl...

melling4• 7 years ago

Learning new environments can be painful so it’s good it starts off easy.

I’m trying to solve them with Swift Playgrounds on the iPad, for example. And I can’t figure out how to create a simple text file for the data.

melling4• 7 years ago

I solved the first part using the examples. Swift is nice.

   func calcFuel(_ mass:Int) -> Int {mass / 3 - 2}

   let z0 = massList.map(calcFuel).reduce(0, +)

or simply ...

   let z1 = massList.map({$0 / 3 - 2}).reduce(0, +)

Any idea how to read the data on the iPad?

brantonb2• 7 years ago

I started last year using Swift Playgrounds. I was lazy and just pasted the input into a multi-line string. I had to switch away from Playgrounds after a couple of days because it would crash due to memory issues. It traces every line of execution and the intermediate values of all variables. I really enjoyed doing the challenges in Swift, but I did have to switch to using my Mac to do it.

This year, I’m learning Python by using a Raspberry Pi 4 directly connected to my iPad via USB. Should be another fun month!

duckarmada• 7 years ago

I've been creating multiline strings and then just using components(separatedBy:)

dmitriid2• 7 years ago

I couldn't figure it out on a Mac. Then I Googled it, and decided I'm better off solving this in languages I know (whatever I feel like today: JS, Python, Java, perhaps even Erlang) or in a language that has a reasonable standard library (Rust) than in this mess: https://twitter.com/dmitriid/status/1201441652507844608

sammorrowdrums3• 7 years ago

I use pastebin raw and get stuff from web requests sometimes rather than local files.

rb808• 7 years ago

lol I actually did this typing into source comma down comma down comma... Only after reading this I realized how lazy I was so went back to do it properly. :)

znpy• 7 years ago

Many people (including myself) use these as an opportunity to try out learning a new language

I hadn't thought about that! I'll take this as an opportunity to learn Rust!

jzymbaluk• 7 years ago

I'm doing the same thing this year!

sammorrowdrums3• 7 years ago

Checking back in - have you done it, is it going OK?

I can't do it when the puzzles come out (too late in UK) but I've really enjoyed Rust so far and I got my 10 stars so far.

Results are really nice, and match and enums etc. really make the language nice.

Rust really has taken many of the best parts of Python, functional paradigms, and lower level languages, and the compiler errors - being warned about missing branches in matches! I'm hoping that finishing 2019 with Rust will lead to more in 2020!

kitd• 7 years ago

Good idea.

I have used http://www.https://cryptopals.com/ for a similar purpose, with the added benefit of learning about cryptography as a parallel outcome.

maremp• 7 years ago

Poorly formatted link, it should be https://cryptopals.com/.

zeveb• 7 years ago

The puzzle itself wasn't very difficult, you could do it by hand if you really wanted to, but it required you to know how to read and parse lines in a file, handle compound data structures, iterate through, and perform basic operations (floor, casting strings to ints, etc).

I don't believe that it required any compound data structures, just looping through the lines in the file.

You're right about the rest, though.

ahaferburg2• 7 years ago

It's faster to just paste the input into your favorite editor, and massage it gently until it is a literal in the language you're using. No parsing necessary.

sergiotapia4• 7 years ago

I’m finally going to attempt it this year. Using elixir here: https://github.com/sergiotapia/advent-of-code-2019-elixir

_v7gu3• 7 years ago

Last year I started out using elixir, but I got filtered due to the goblins...

sergiotapia4• 7 years ago

What does this mean?

jammygit• 7 years ago

These are daily programming puzzles? How long do they take on average?

Also, I know somebody who is just starting out at coding. Would it be too hard for them? They are brand new, learning about loops

j1elo• 7 years ago

I wondered the same, also thinking about people I know who are starting to program.

In the end I think it's not a good fit, given that basic concepts are still being understood, and the mere task of reading a file and iterating over the lines, even the concept itself of what "iterating" is, is already a big challenge...

Trying is free and won't hurt, though, so why not :)

teraflop2• 7 years ago

I completed the whole thing last year; the problems start out very easy, but get dramatically more challenging over the course of the month. Check out the statistics for how many people completed each problem in 2018: https://adventofcode.com/2018/stats

The first few problems are approachable by pretty much anyone who understands how to do arithmetic, file I/O and basic flow control. Many of the later problems require advanced skills such as more sophisticated algorithms (graph theory, dynamic programming, etc.), reverse engineering, and careful debugging.

For what it's worth, I would expect anyone who knows what a loop is to be able to get the first half of today's problem without much difficulty. The second half is a bit less trivial but also pretty easy to understand.

ken• 7 years ago

Check out the statistics for how many people completed each problem in 2018

I suspect you'd see a dropoff like this regardless of whether the problems get more difficult or not. Going to the gym doesn't get any harder in February but they see the same effect.

Arnavion• 7 years ago

In general the puzzles involve basic operations that any language would have. Functions, data structures, recursion, some amount of back-and-forth between strings and numbers and records. There isn't any reliance on library-like things like making HTTP requests or parsing complex file formats. I think they would be fine for someone starting out at coding.

Every day's puzzle has two parts. The first part is usually easy. The second part is then a twist that requires a change to the solution of the first part.

Apart from that, you can always skip a day if you just can't solve it. The exception is that sometimes a puzzle can reference the solution of an older day, so if you'd solved the older day you would already have an understanding of how to proceed, and might be able to reuse some code.

gbear6052• 7 years ago

I think they would be fine for someone starting out at coding.

The earlier ones, perhaps, but professional programmers struggle with the later ones. I’d never suggest that some one new to programming tries to do all of AoC.

IbyvzOneoneh• 7 years ago

They take <15min - >2h

First couple of tasks are really easy, but difficulty increases over time and so does time needed to solve them.

Someone who is currently learning about loops might not be able to solve these on their own, but with someone else's help they might learn lots of useful concepts (e.g. linked lists, bfs, basic asm, how to code efficiently...) and try to apply them.

AoC are solving usually those who are quite familiar with programming and want to learn a new language or to compete with colleagues.

sergiotapia4• 7 years ago

For someone just starting out they would get stuck on this very first problem, it involves recursion. People 'get' recursion, but coding it is something different.

gbear6052• 7 years ago

It doesn’t need recursion, you can do a while(round(x/3)-2 > 0) type thing, but recursion is simpler.

empath752• 7 years ago

I just knocked out a non-recursive solution in 9 lines of python in five minutes.

loeg4• 7 years ago

If you're medium fast, they start out in the single digit or tens of minutes range and ramp up to some 60+ minute puzzles the last handful of days (but also some 20 minute puzzles, it varies a lot).

I haven't done it since 2017, and I was pretty quick (made that year's overall leaderboard), but on average they took me about 23 minutes (for both parts).

thethirdone• 7 years ago

I was doing a little of catching up on older problems to improve my speed to get on the leaderboard and I found that the fastest way to finish one problem was to use oeis.

After seeing the problem [0], I didn't immediately think to use oeis because the manhatten distance of a spiral is pretty easy to code or do by hand. The second stage has a harder sequence though. It prompted me to check oeis and I easily got the answer [2] within a minute of checking.

Looking back at the first stage, I found a sequence for it [1] and PARI/GP code i could run to answer the question. If I had used oeis immediately I would have a solution to both phases in 2 minutes which would be the fastest on the old leaderboard for the problem [3].

[0] https://adventofcode.com/2017/day/3

[1] https://oeis.org/A214526

[2] https://oeis.org/A141481

[3] https://adventofcode.com/2017/leaderboard/day/3

loeg4• 7 years ago

I had plenty of 20-20 hindsight about faster ways to have solved puzzles in the past. I don't know if I was ever #1 on any day on either star. I think I might've been top 10, on one star, of one day, once.

coolreader18• 7 years ago

Wow, what a great distraction for students to have during finals season! ;)

messe• 7 years ago

Self promotion, but as this is my first year doing advent of code I'm solving all of the problems using awk[1], the solutions will be published here[2]

[1] https://man.openbsd.org/awk

[2] https://jo.ie/advent-of-awk-2019.html

cfors• 7 years ago

With respect to the fact that 99% of my use of awk is done like this:

  > | awk '{print $<word>}'

The solution to the first exercise looks surprisingly clean. It will be interesting to see how they continue as the challenges get harder. Bookmarked!

bewuethr• 7 years ago

I've used awk for one year of Advent of Code: https://github.com/bewuethr/advent-of-code/tree/master/2016

Some problems feel like they were designed to be solved in awk, like the assembly style ones. Others, not so much... But it was great fun overall and I learned a lot about awk.

mathw3• 7 years ago

As someone using a completely mainstream and normal language (well, Rust), I salute you.

malloreon2• 7 years ago

I like everything about this except the name.

the word advent is religious.

jimmyswimmy• 7 years ago

The name is reminiscent of an advent calendar, which traditionally has a labeled door behind which is a piece of candy, small toy or other trinket. These calendars are intended for young children to remind them of the period of advent.

If you are religious, look upon this as a similar thing which reminds you of the season, building in anticipation of the final day.

If you are not religious, it's just a word with no special meaning other than the time of year. Same goes if you are not of a Christian religion.

bkromhout• 7 years ago

This is only true when it's used as a proper noun; in which case, yes, it refers one of two things in the context of Christianity.

Otherwise, it's just a normal word which means "the arrival of a notable person, thing, or event".

p1necone• 7 years ago

And?

malloreon2• 7 years ago

if this is a religious project, it should be clearly marked as such.

if it's not, why not use a nonreligious word?

dang2• 7 years ago

Please don't take HN threads into religious flamewar.

https://news.ycombinator.com/newsguidelines.html

dom96• 7 years ago

This event is a really nice way to try out new programming languages. You can easily find many people doing the challenges in various languages and communities coming together to work through the problems together. It’s also very interesting seeing how each person solves the problem in their favourite language.

For example, here is the Nim communities effort: https://forum.nim-lang.org/t/5588

andonisus• 7 years ago

Here is my solution to Day 1 Part 2 in Go: https://play.golang.com/p/SQsCdTXk_YH

sircastor• 7 years ago

I went to bed before trying it last night, but couldn't sleep. So I did the day one problem early this morning. It was fun, and went quicker than I thought. I guess I must've improved from last year.

sidcool• 7 years ago

Does anybody know how the scoring system works for AoC?

vpzom• 7 years ago

See https://adventofcode.com/2019/leaderboard

qznc2• 7 years ago

I'm trying to use J and still struggle with the second part of day 1. Any other J users?

macintux• 7 years ago

If you haven't already found the discussion, Reddit is very active and very helpful. Seems to be the primary water cooler for the event.

https://www.reddit.com/r/adventofcode/

valec• 7 years ago

I'd argue /g/ on 4chan is actually. 3-4 threads get filled a day (~300 replies each).

It's honestly the only real reason to go on /g/ (or really 4chan in general) for me.

JaumeGreen• 7 years ago

I have found a solution someone posted [0]

It looks similar to what I though I had to write, but I will have to reread it and the documentation to understand it well.

And day 2 seems a bit too complex with my meager J knowledge. OTOH with the J interpreter for android and its terseness it seems the most suited language for programming on a phone, so I will probably stick to it.

[0] https://www.reddit.com/r/adventofcode/comments/e4axxe/2019_d...

qznc2• 7 years ago

I'm actually surprise how many J/APL/K/Q solutions get posted there already. It seems to be popular among golfers.

ph2082• 7 years ago

Jeez, tension is real. Specially if you are thinking about cracking top 100. Competition is a b.

Lot of fun though.

mathw3• 7 years ago

That's only possible if you live in the correct time zone, too.

sunaden• 7 years ago

If someone is interested in the previous years of Advent of Code they are available as notebooks in Peter Norvig's pytudes repository: https://github.com/norvig/pytudes

narimiran• 7 years ago

Thank you very much for this!

I was aware of Norvig's 2016 AoC solutions, but I thought he never did any of the newer editions. I know what I'll be reading today :)

janvdberg• 7 years ago

Advent of Code is a lot of fun! Last year I wrote a little bit about all the different languages/approaches people use to solve the challenges: https://j11g.com/2018/12/03/advent-of-code/

LandR3• 7 years ago

Day 2 part 2, what is it actually asking?

I can't tell from the description what the actual puzzle is...

Is it that I need to generate a program that generates the output 19690720 when run through the function that was written in part 1?

eachro• 7 years ago

In the first problem they told you what numbers to put in position 1 and 2. In the second problem you want to find the specific numbers for position 1 and 2 that yield the desired output.

LandR3• 7 years ago

Ah ok, thanks!

My reading comprehension obviously needs some work :P

bsdnoob• 7 years ago

you need to find value of memory[1] & memory[2] where memory is the program from first part, which gets you 19690720

LandR3• 7 years ago

Thanks, five minutes to write the code and get an answer, half an hour staring at it wondering what on earth I was actually supposed to do....

Feel like a bit of an idiot.

dbetteridge• 7 years ago

Would appreciate feedback on my Go code!

I'm sure theres a better way to approach some of these.

https://danielbetteridge.com/advent-of-code-day-1/

Kinrany• 7 years ago

The third puzzle mentions Halt and Catch Fire, a brilliant TV show about innovation and the lives of the (fictional) people behind it.

daveFNbuck• 7 years ago

It actually references the thing that the show is named after. If you click on the link, it's not about the show.

Advent of Code 2019

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