73 lines
2.3 KiB
Haskell
73 lines
2.3 KiB
Haskell
module Day4 where
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import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
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import Data.Text (splitOn, unpack, pack)
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import Prelude hiding (splitAt)
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type Board = [[Int]]
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column :: Board -> Int -> [Int]
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column board i = map (!! i) board
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splitAt :: String -> String -> [String]
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splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str
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-- remove padding spaces and turn a board line into ints
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lineToInts :: String -> [Int]
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lineToInts str = map read $ filter (/= "") $ splitAt " " str
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isLineWinning :: [Int] -> [Int] -> Bool
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isLineWinning nums = all (`elem` nums)
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-- in: random numbers, board
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-- out: only unmarked numbers in board
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unmarkedNums :: [Int] -> Board -> Board
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unmarkedNums nums = map (filter (`notElem` nums))
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-- in: random numbers, board
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-- out: sum of all unmarked numbers
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unmarkedSum :: [Int] -> Board -> Int
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unmarkedSum nums board = sum . concat $ unmarkedNums nums board
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-- in: board, list of random numbers
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-- out: true if board won
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checkBoard :: Board -> [Int] -> Bool
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checkBoard board nums = any (isLineWinning nums) allLines
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where
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allLines = board ++ map (column board) [0..4]
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-- in: list of boards, list of random numbers
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-- out: board that won, number of iterations
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checkBoards' :: [Board] -> [Int] -> (Board, Int)
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checkBoards' [] nums = ([], length nums)
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checkBoards' (x:xs) nums
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| checkBoard x nums = (x, length nums)
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| otherwise = checkBoards' xs nums
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-- in: list of boards, list of random numbers
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-- out: board that won, number of iterations
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-- will error if none of the tables are solvable
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checkBoards :: [Board] -> [Int] -> Int -> (Board, Int)
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checkBoards boards nums iter
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| null $ fst $ checkBoards' boards list = checkBoards boards nums (iter + 1)
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| otherwise = checkBoards' boards list
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where
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list = take iter nums
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main :: IO ()
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main = do
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input <- openFile "inputs/4.txt" ReadMode
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contents <- hGetContents input
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-- random numbers from the first line
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let list = map read $ splitAt "," $ head $ splitAt "\n\n" contents :: [Int]
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-- the remaining lines are bingo boards
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let bingus = map lines $ tail $ splitAt "\n\n" contents
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let boards = map (map lineToInts) bingus
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let (board, num) = checkBoards boards list 1
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let sum = unmarkedSum (take num list) board
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print $ sum * list !! (num - 1)
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hClose input
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