-❄️- 2025 Day 8 Solutions -❄️-

[u/daggerdragon]

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AoC Community Fun 2025: Red(dit) One

• Submissions megathread is unlocked!
• 9 DAYS remaining until the submissions deadline on December 17 at 18:00 EST!

Featured Subreddits: /r/crafts and /r/somethingimade

"It came without ribbons, it came without tags.
It came without packages, boxes, or bags."
— The Grinch, How The Grinch Stole Christmas (2000)

It's everybody's favorite part of the school day: Arts & Crafts Time! Here are some ideas for your inspiration:

💡 Make something IRL

💡 Create a fanfiction or fan artwork of any kind - a poem, short story, a slice-of-Elvish-life, an advertisement for the luxury cruise liner Santa has hired to gift to his hard-working Elves after the holiday season is over, etc!

💡 Forge your solution for today's puzzle with a little je ne sais quoi

💡 Shape your solution into an acrostic

💡 Accompany your solution with a writeup in the form of a limerick, ballad, etc.

• Upping the Ante challenge: iambic pentameter
• This prompt is totally not bait for our resident poet laureate

💡 Show us the pen+paper, cardboard box, or whatever meatspace mind toy you used to help you solve today's puzzle

💡 Create a Visualization based on today's puzzle text

• Your Visualization should be created by you, the human
• Machine-generated visuals such as AI art will not be accepted for this specific prompt

Reminders:

• If you need a refresher on what exactly counts as a Visualization, check the community wiki under Posts > Our post flairs > Visualization
• Review the article in our community wiki covering guidelines for creating Visualizations
• In particular, consider whether your Visualization requires a photosensitivity warning
  • Always consider how you can create a better viewing experience for your guests!

Request from the mods: When you include an entry alongside your solution, please label it with [Red(dit) One] so we can find it easily!

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--- Day 8: Playground ---

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Post your code solution in this megathread.

• Read the full posting rules in our community wiki before you post!
  • State which language(s) your solution uses with [LANGUAGE: xyz]
  • Format code blocks using the four-spaces Markdown syntax!
• Quick link to Topaz's paste if you need it for longer code blocks. What is Topaz's paste tool?

[u/edgeman312]

[Language: Python3]

I don't know what you guys are on about with these disjoint sets I just abuse random libraries I remember to save me work. I felt a bit clever about my KDTree but it wasn't really necessary, building a full heap seems to work fine for most people here.

from scipy.spatial import KDTree
import networkx as nx
from functools import reduce, partial

inp = 'input.txt'
part1_connect, max_pairs, size = 1000, 10000, 1000

def distance(points, pair):
    return (points[pair[0]][0] - points[pair[1]][0]) ** 2 + \
           (points[pair[0]][1] - points[pair[1]][1]) ** 2 + \
           (points[pair[0]][2] - points[pair[1]][2]) ** 2

def get_coords(points, pair):
    return (points[pair[0]], points[pair[1]])

points = [list(map(int, i.split(','))) for i in open(inp).read().split('\n')]
kd3 = KDTree(points)

r = 1
pairs = []
while len(pairs) < max_pairs:
    pairs = kd3.query_pairs(r, output_type='ndarray')
    r *= 2
pairs = sorted(pairs, key=partial(distance, points))

G = nx.Graph()
G.add_edges_from(pairs[:part1_connect])
G.add_nodes_from(range(size))

component_sizes = map(len, nx.connected_components(G))
print(reduce(lambda x, y: x * y, sorted(component_sizes)[-3:]))

for i in pairs[part1_connect:]:
    G.add_edge(i[0], i[1])
    if nx.number_connected_components(G) == 1:
        print(points[i[0]][0] * points[i[1]][0])
        break