Advent Of Code

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An unofficial home for the advent of code community on programming.dev! Other challenges are also welcome!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

Everybody Codes is another collection of programming puzzles with seasonal events.

AoC 2025

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Keep all content related to advent of code in some way
If what youre posting relates to a day, put in brackets the year and then day number in front of the post title (e.g. [2024 Day 10])
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console.log('Hello World')

founded 2 years ago

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hades@programming.dev

🐮 - 2024 DAY 10 SOLUTIONS - 🐮 (programming.dev)

submitted 11 months ago by CameronDev@programming.dev to c/advent_of_code@programming.dev

29 comments fedilink hide all child comments

Day 10: Hoof It

Megathread guidelines

Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
You can send code in code blocks by using three backticks, the code, and then three backticks or use something such as https://topaz.github.io/paste/ if you prefer sending it through a URL

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What is this?: Here is a post with a large amount of details: https://programming.dev/post/6637268
Where do I participate?: https://adventofcode.com/
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[–] ystael@beehaw.org 2 points 11 months ago* (last edited 11 months ago) (1 children)

J

Who needs recursion or search algorithms? Over here in line noise array hell, we have built-in sparse matrices! :)

data_file_name =: '10.data'
grid =: "."0 ,. > cutopen fread data_file_name
data =: , grid
'rsize csize' =: $ grid
inbounds =: monad : '(*/ y >: 0 0) * (*/ y &lt; rsize, csize)'
coords =: ($ grid) &amp; #:
uncoords =: ($ grid) &amp; #.
NB. if n is the linear index of a point, neighbors n lists the linear indices
NB. of its orthogonally adjacent points
neighbors =: monad : 'uncoords (#~ inbounds"1) (coords y) +"1 (4 2 $ 1 0 0 1 _1 0 0 _1)'
uphill1 =: dyad : '1 = (y { data) - (x { data)'
uphill_neighbors =: monad : 'y ,. (#~ (y &amp; uphill1)) neighbors y'
adjacency_of =: monad define
   edges =. ; (&lt; @: uphill_neighbors"0) i.#y
   NB. must explicitly specify fill of integer 0, default is float
   1 edges} 1 $. ((#y), #y); (0 1); 0
)
adjacency =: adjacency_of data
NB. maximum path length is 9 so take 9th power of adjacency matrix
leads_to_matrix =: adjacency (+/ . *)^:8 adjacency
leads_to =: dyad : '({ &amp; leads_to_matrix) @: &lt; x, y'
trailheads =: I. data = 0
summits =: I. data = 9
scores =: trailheads leads_to"0/ summits
result1 =: +/, 0 &lt; scores
result2 =: +/, scores

[–] sjmulder@lemmy.sdf.org 2 points 11 months ago* (last edited 11 months ago) (1 children)

For some reason the code appears to be HTML escaped (I'm using the web interface on https://lemmy.sdf.org)

[–] ystael@beehaw.org 2 points 11 months ago* (last edited 11 months ago)

Yes. I don't know whether this is a beehaw specific issue (that being my home instance) or a lemmy issue in general, but < and & are HTML escaped in all code blocks I see. Of course, this is substantially more painful for J code than many other languages.