65 lines
2.3 KiB
Haskell
65 lines
2.3 KiB
Haskell
import Data.List
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import Data.Maybe
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type Position = (Int,Int)
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type Entry = (Maybe Int, Int)
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type MatrixMap = [(Position, Entry)]
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parse :: Int -> Int -> String -> MatrixMap
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parse x y []=[]
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parse x y ('\n':xs)=parse 0(y+1)xs
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parse x y ('S':xs)=((x,y),(Just 0,fromEnum 'a')):parse(x+1)y xs
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parse x y ('E':xs)=((x,y),(Nothing,fromEnum 'z')):parse(x+1)y xs
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parse x y (i:xs)=((x,y),(Nothing,fromEnum i)):parse(x+1)y xs
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parse2 x y []=[]
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parse2 x y ('\n':xs)=parse2 0(y+1)xs
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parse2 x y ('S':xs)=((x,y),(Nothing,fromEnum 'a')):parse2(x+1)y xs
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parse2 x y ('E':xs)=((x,y),(Just 0,fromEnum 'z')):parse2(x+1)y xs
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parse2 x y (i:xs)=((x,y),(Nothing,fromEnum i)):parse2(x+1)y xs
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s = f(0,0)'S'
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e = f(0,0)'E'
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f :: Position -> Char-> String -> Position
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f(x,y)i(h:t)|h==i=(x,y)|'\n'==h=f(0,y+1)i t|let=f(x+1,y)i t
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lookup2 i p = lookup i p >>= \x->pure(i, x)
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valuesSurrounding :: Position -> MatrixMap -> [(Position, Entry)]
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valuesSurrounding (x,y)pos|Just (Just d,h)<-lookup (x,y) pos
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= map (\(p,(_,i))->(p,(Just (d+1), i))) $ filter((==Nothing).fst.snd) $ filter((<=h+1).snd.snd) $ catMaybes $ map(`lookup2`pos) [(x,y-1),(x,y+1),(x+1,y),(x-1,y)]
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valuesSurrounding2 :: Position -> MatrixMap -> [(Position, Entry)]
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valuesSurrounding2 (x,y)pos|Just (Just d,h)<-lookup (x,y) pos
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= map (\(p,(_,i))->(p,(Just (d+1), i))) $ filter((==Nothing).fst.snd) $ filter((>=h-1).snd.snd) $ catMaybes $ map(`lookup2`pos) [(x,y-1),(x,y+1),(x+1,y),(x-1,y)]
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doStuff :: MatrixMap -> [(Position, Entry)] -> MatrixMap
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doStuff i [] = i
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doStuff i (x:t)|n<-valuesSurrounding (fst x) i=doStuff (foldr update i n) (t++n)
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doStuff2 :: MatrixMap -> [(Position, Entry)] -> MatrixMap
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doStuff2 i [] = i
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doStuff2 i (x:t)|n<-valuesSurrounding2 (fst x) i=doStuff2 (foldr update i n) (t++n)
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update :: (Position, Entry) -> MatrixMap -> MatrixMap
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update x m|Just entry<-lookup (fst x) m, Just idx<-elemIndex (fst x,entry) m,(h,c:t)<-splitAt idx m = h++x:t
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p1 f = do
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x <- readFile f
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let m = parse 0 0 x
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let Just start = lookup2 (s x) m
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let d = doStuff m [start]
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let end = lookup2 (e x) d
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print end
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p2 f = do
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x <- readFile f
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let m = parse2 0 0 x
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let Just start = lookup2 (e x) m
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let d = doStuff2 m [start]
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let (Just f, _) = head$sort$map snd$filter (\(p,(i,q))->q==97 && i /= Nothing) d
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print f
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main=p1 "day12long" >> p2 "day12long"
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