WIP AOC 2022 & 2023

AOC2023/src/Day09.hs

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+module Day09 (day09) where
+
+import Data.List.Split (splitOn)
+
+parseLine :: String -> [Int]
+parseLine i = map read $ splitOn " " i
+
+getDifferences :: [Int] -> [Int]
+getDifferences [] = []
+getDifferences [_] = []
+getDifferences (h:t@(th:_)) = (th - h) : getDifferences t
+
+listIsZeros :: [Int] -> Bool
+listIsZeros = all (== 0)
+
+getIterations :: [Int] -> [[Int]]
+getIterations a = takeWhile (not . listIsZeros) $ iterate getDifferences a
+
+getNextItem :: [Int] -> Int -> Int
+getNextItem l incr = last l + incr
+
+getNextItems :: [[Int]] -> Int
+getNextItems = foldr getNextItem 0
+
+getPrevItem :: [Int] -> Int -> Int
+getPrevItem l incr = head l - incr
+
+getPrevItems :: [[Int]] -> Int
+getPrevItems = foldr getPrevItem 0
+
+day09 :: IO ()
+day09 = do
+  putStrLn "AOC 2023 day 09"
+  input <- getContents
+  let input' = map parseLine $ lines input
+  putStrLn "Part1"
+  print $ sum $ map (getNextItems . getIterations) input'
+  putStrLn "Part2"
+  print $ sum $ map (getPrevItems . getIterations) input'