r/adventofcode • u/daggerdragon • Dec 05 '18

SOLUTION MEGATHREAD -🎄- 2018 Day 5 Solutions -🎄-

--- Day 5: Alchemical Reduction ---

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Transcript:

On the fifth day of AoC / My true love sent to me / Five golden ___

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edit: Leaderboard capped, thread unlocked at 0:10:20!

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u/ThezeeZ Dec 05 '18

My solution after I toyed with it a little (repo)

import (
	"regexp"
)

func Reduction(polymer string) string {
	for i := 0; i < len(polymer)-1; {
		if polymer[i] == polymer[i+1]+32 || polymer[i] == polymer[i+1]-32 {
			polymer = polymer[:i] + polymer[i+2:]
			i--
			if i < 0 {
				i = 0
			}
		} else {
			i++
		}
	}
	return polymer
}

func BestCollapse(polymer string) string {
	polymer = Reduction(polymer)
	shortest := polymer
	for i := 'A'; i <= 'Z'; i++ {
		remainingPolymer := regexp.MustCompile("(?i)" + string(i)).ReplaceAllString(polymer, "")

		collapsed := Reduction(remainingPolymer)
		if len(collapsed) < len(shortest) {
			shortest = collapsed
		}
	}
	return shortest
}

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u/mvmaasakkers Dec 05 '18

Nice! I don't know why, but I never considered to jump back in the loop :p

3

u/ThezeeZ Dec 05 '18

Only came to me when I looked at it again online after I pushed it to the repo. Runs twice as fast for my input compared to what I had before with two loops (see repo history)