Advent Of Code

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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.

AoC 2024

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🌻 - 2024 DAY 12 SOLUTIONS -🌻 (programming.dev)

submitted 1 week ago by [email protected] to c/[email protected]

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Day 12: Garden Groups

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[–] [email protected] 4 points 1 week ago* (last edited 1 week ago) (6 children)

Uiua

~~Takes about 3 seconds to solve both parts for live data, caused primarily by my terrible fill function in FieldCoords which repeatedly refills and dedups already discovered cells. I promised myself when I wrote it that I would revisit it, but I really can't be bothered right now. Sorry Kai.~~

LATE EDIT: Thanks to Quant for the inspiration to revisit this. With his code snippet and the realisation that I should normalise all fields to remove wasted space, runtime is now down to 55ms.

Data ← ⊜∘⊸≠@\n "AAAA\nBBCD\nBBCC\nEEEC"
N₄     ← [¯1_0 1_0 0_¯1 0_1]               # Four orthogonal neighbours.
Fences ← /+/+=0≡(⬚0⊡+N₄¤)⊙¤⊚.°⊚            # Fences for a field, by looking for edges.
Cs     ← [0 1 1 0 1 0 2 1 1 2 0 1 0 1 1 0] # Number of corners keyed by bitarray of 2x2 grid.
Sides  ← /+♭⬚0⧈(⊡:Cs°⋯♭)2_2°⊚              # Add border, look for corners in 2x2 windows.

# Use `classify` to find fields, then normalise to 0_0.
Fields ← ≡⍚(-¤⊸/↧)⊜□:⇡△.+1⍜♭⊛Data # Thanks to Quant!

/+×≡◇⊃⧻Fences Fields
/+×≡◇⊃⧻Sides Fields

[–] [email protected] 2 points 1 week ago (1 children)

I found multidimensional markers for partition to work really well for finding the fields: Areas ← ⊜□:⇡△.+1⍜♭⊛ It just groups the other array's contents according to adjacent markers, horizontally and vertically. Took me quite a bit to figure out what's actually happening in the example in the documentation ^^'

[–] [email protected] 2 points 1 week ago* (last edited 1 week ago) (1 children)

Ooh, interesting, I'll have to give that a try. Thanks!

(edit) Wow, that replaced my three lines of overly complex code without a hitch. classify is an operator I never really got the point of before. Beautiful.

Data ← ⊜∘⊸≠@\n "AAAA\nBBCD\nBBCC\nEEEC"
N₄     ← [¯1_0 1_0 0_¯1 0_1]               # Four orthogonal neighbours.
Fences ← /+≡(/+=0⬚0⊡+N₄¤)⊙¤⊚.°⊚            # Fences for a field, by looking for edges.
Cs     ← [0 1 1 0 1 0 2 1 1 2 0 1 0 1 1 0] # Number of corners keyed by bitarray of 2x2 grid.
Sides  ← /+/+⧈(⊡:Cs°⋯♭)2_2⌝↘¯1_¯1⌝↘1_1°⊚   # Add border, look for corners in 2x2 windows.

Fields ← ⊜□:⇡△.+1⍜♭⊛Data

/+×≡◇⊃⧻Fences Fields
/+×≡◇⊃⧻Sides Fields

[–] [email protected] 2 points 1 week ago (1 children)

Nice :D
How's the speed now?

[–] [email protected] 2 points 1 week ago* (last edited 1 week ago) (1 children)

1.8s now. 99% of that in Sides. I've just had an idea though... ~~maybe too late for today though!~~

edit: prepending ≡⍚(-¤⊸/↧) toFields spared me from manipulating hundreds of irrelevant 0's, so time is very good now at 55ms.

[–] [email protected] 2 points 6 days ago (1 children)

Damn that's a lot time saved. I love how unassuming the addition looks for how great an effect it has

[–] [email protected] 1 points 6 days ago

It was a real D'oh! moment when I visualised the data I was generating and saw all the zeros stretching across the page.

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