Day 4

Day4.hs

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

Day4_1.hs

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+module Day4_1 where
+import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
+import Data.Text (splitOn, unpack, pack)
+import Prelude hiding (splitAt)
+
+type Board = [[Int]]
+
+column :: Board -> Int -> [Int]
+column board i = map (!! i) board
+
+splitAt :: String -> String -> [String]
+splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str
+
+-- remove padding spaces and turn a board line into ints
+lineToInts :: String -> [Int]
+lineToInts str = map read $ filter (/= "") $ splitAt " " str
+
+isLineWinning :: [Int] -> [Int] -> Bool
+isLineWinning nums = all (`elem` nums)
+
+-- in: random numbers, board
+-- out: only unmarked numbers in board
+unmarkedNums :: [Int] -> Board -> Board
+unmarkedNums nums = map (filter (`notElem` nums))
+
+-- in: random numbers, board
+-- out: sum of all unmarked numbers
+unmarkedSum :: [Int] -> Board -> Int
+unmarkedSum nums board = sum . concat $ unmarkedNums nums board
+
+-- in: board, list of random numbers
+-- out: true if board won
+checkBoard :: Board -> [Int] -> Bool
+checkBoard board nums = any (isLineWinning nums) allLines
+    where
+        allLines = board ++ map (column board) [0..4]
+
+-- in: list of boards, list of random numbers
+-- out: boards that won, number of iterations
+checkBoards' :: [Board] -> [Int] -> [(Board, Int)] -> [(Board, Int)]
+checkBoards' [] nums acc = acc
+checkBoards' (x:xs) nums acc
+    | checkBoard x nums = checkBoards' xs nums (acc ++ [(x, length nums)])
+    | otherwise = checkBoards' xs nums acc
+
+checkBoards :: [Board] -> [Int] -> [(Board, Int)]
+checkBoards boards nums = filter (\x -> fst x /= []) solutions
+    where solutions = [ k |  i <- [1..length nums],
+                             let j = take i nums,
+                             k <- checkBoards' boards j [] ]
+
+dedup :: Eq a => [(a, b)] -> [(a, b)]
+dedup [] = []
+dedup (x:xs) = x : dedup (filter (\y -> fst x /= fst y) xs)
+
+main :: IO ()
+main = do
+    input <- openFile "inputs/4.txt" ReadMode
+    contents <- hGetContents input
+
+    -- random numbers from the first line
+    let list = map read $ splitAt "," $ head $ splitAt "\n\n" contents :: [Int]
+    -- the remaining lines are bingo boards
+    let bingus = map lines $ tail $ splitAt "\n\n" contents
+    let boards = map (map lineToInts) bingus
+
+    let (board, num) = last . dedup $ checkBoards boards list
+
+    let sum = unmarkedSum (take num list) board 
+    print $ sum * list !! (num - 1)
+
+    hClose input