this post was submitted on 08 Dec 2025
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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.
EC 2025
AoC 2025
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| M | T | W | T | F | S | S |
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| 8 | 9 | 10 | 11 | 12 |
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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])
- When an event is running, keep solutions in the solution megathread to avoid the community getting spammed with posts
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My initial approach was to consider each junction as a circuit, and then merge the closest circuits. Took me way to long to realize the problem statement for part 1 made this unworkable (as you need to count redundant connections as "attempts"). Thankfully part 2 doesn't care about how many connections you make, so I was able to reuse that code to solve part 2.
To solve part 1 "the right way", I first thought I had to store a circuit as a collection of pairs of junctions (literally, the collection of connections). Oh god was that messy code; 3 layers of nested for-loops and it still wasn't getting close to the answer. I eventually realized I could reference the junctions' indices in the input to simplify things, allowing me to manipulate simple sets of ints. Combine with pre-calculating the distances once before starting the connecting/merging and you end up with a surprisingly simple and snappy algorithm.
Given I realized these optimizations after restarting part 1, my solution for part 2 doesn't take advantage of any of them and takes an eye-watering 22 seconds to terminate on average. It probably re-computes more distances than it computes new ones, for each iteration...
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