advent-2021/4/solution.hs

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{-# LANGUAGE TupleSections #-}
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import Data.List (transpose, partition)
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main :: IO ()
main = readFile "4/input.txt" >>= print . solve . parse . lines
type Input = ([Int], [Board])
parse :: [String] -> Input
parse (l : ls) = (n, b)
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where n = map read $ words [ if c == ',' then ' ' else c | c <- l ]
b = parseBoards (filter (/= "") ls)
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parseBoards :: [String] -> [Board]
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parseBoards [] = []
parseBoards l = parse a : parseBoards b
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where (a,b) = splitAt 5 l
parse = map $ map ((,False) . read) . words
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type Board = [[Cell]]
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hasWon :: Board -> Bool
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hasWon b = check b || check (transpose b)
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where check = any $ all marked
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score :: Int -> Board -> Int
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score n b = n * sum [ x | c <- b, (x, False) <- c ]
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call :: Int -> Board -> Board
call n = map (map mark)
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where mark (x,s) = (x, s || x == n)
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type Cell = (Int, Bool)
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marked :: Cell -> Bool
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marked = snd
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solve :: Input -> (Int, Int)
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solve (n, b) = (head r, last r)
where r = map (uncurry score) $ bingo n b
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bingo :: [Int] -> [Board] -> [(Int, Board)]
bingo _ [] = []
bingo (n : ns) (b : bs) = map (n,) w ++ bingo ns l
where (w,l) = partition hasWon r
r = iter n (b : bs)
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iter :: Int -> [Board] -> [Board]
iter _ [] = []
iter n (b : bs) = call n b : iter n bs