Advent Of Code

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An unofficial home for the advent of code community on programming.dev!

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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🎁 - 2023 DAY 5 SOLUTIONS -🎁 (self.advent_of_code)

submitted 11 months ago* (last edited 11 months ago) by Ategon to c/advent_of_code

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Day 5: If You Give a Seed a Fertilizer

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)
Code block support is not fully rolled out yet but likely will be in the middle of the event. Try to share solutions as both code blocks and using something such as https://topaz.github.io/paste/ , pastebin, or github (code blocks to future proof it for when 0.19 comes out and since code blocks currently function in some apps and some instances as well if they are running a 0.19 beta)

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[–] [email protected] 5 points 11 months ago (1 children)

I got far enough to realize that you probably needed to work backwards and given a location, determine the accompanying seed, and then check if that seed is one of the ones listed in the range. Still though, starting at 0 for location and working up was taking forever to find the first valid seed

Someone in this thread pointed out that if you picked the first value of each range in the map, working backwards from those points will get you a short list of seeds which map to low values. You then check if those seeds are valid, and also check the location of the first seeds in the range (the rest of the seeds in the range don't matter because those are covered by the first check). This ends up with about 200 locations which you can sort, to get the lowest value.

[–] [email protected] 3 points 11 months ago

I tried brute forcing it but couldn't get the process to finish. Iterating through hundreds of millions of seeds is no bueno.

After reading your comment though I got the idea to map whole seed ranges instead of individual seeds. That finished in no time of course.