AoC/2019/day6/day6.hs

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import Data.List.Split
import Data.List
import Data.Maybe
main = do
content <- (map (splitOn ")") . lines) <$> readFile "input"
print $ day6a content
print $ day6b content
day6a l = sum $ map (day6a' (transpose l) l) l
day6a' l l2 (s:t)
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| s `elem` (l!!1) = 1 + day6a' l l2 next_pair
| otherwise = 1
where next_pair = l2 !! (fromJust $ elemIndex s (l!!1))
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day6b :: [[String]] -> Int
day6b l = day6b' l "YOU" "SAN" [] - 2
day6b' l s t visited
| [s,t]`elem`l||[t,s]`elem`l=1
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| otherwise = 1 + minimum next_nodes
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where neighbours a = filter (/=a) $ concat
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[if x==a then xs else [] | xs<-l, x<-xs]
next_nodes = [if x `elem` visited then maxBound -1
else day6b' l x t (x:visited)| x<-neighbours s]