2023-01 in haskell

1 files changed, 78 insertions, 0 deletions

diff --git a/2023/1-Trebuchet/second.hs b/2023/1-Trebuchet/second.hs
new file mode 100644
index 0000000..3bcfa06
--- /dev/null
+++ b/2023/1-Trebuchet/second.hs
@@ -0,0 +1,78 @@
+-- requires cabal install --lib megaparsec parser-combinators
+module Main (main) where
+import Control.Monad (void, when)
+import Data.Char qualified as C
+import Data.Functor
+import Data.List qualified as L
+import Data.Map qualified as M
+import Data.Maybe
+import Data.Set qualified as S
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+
+exampleExpectedOutput = 281
+
+type Input = [(Int, Int)]
+
+type Parser = Parsec Void String
+
+parseDigit :: Parser Int
+parseDigit = (C.digitToInt <$> digitChar)
+         <|> (string "one" $> 1)
+         <|> (string "two" $> 2)
+         <|> (string "three" $> 3)
+         <|> (string "four" $> 4)
+         <|> (string "five" $> 5)
+         <|> (string "six" $> 6)
+         <|> (string "seven" $> 7)
+         <|> (string "eight" $> 8)
+         <|> (string "nine" $> 9)
+         <|> (letterChar *> parseDigit)
+
+parseDigitReversed :: Parser Int
+parseDigitReversed = (C.digitToInt <$> digitChar)
+                 <|> (string "eno" $> 1)
+                 <|> (string "owt" $> 2)
+                 <|> (string "eerht" $> 3)
+                 <|> (string "ruof" $> 4)
+                 <|> (string "evif" $> 5)
+                 <|> (string "xis" $> 6)
+                 <|> (string "neves" $> 7)
+                 <|> (string "thgie" $> 8)
+                 <|> (string "enin" $> 9)
+                 <|> (letterChar *> parseDigitReversed)
+
+parseFirstAndLast :: String -> (Int, Int)
+parseFirstAndLast str = (f, l)
+  where
+    f = case runParser parseDigit "parseDigit" str of
+      Left bundle -> error $ errorBundlePretty bundle
+      Right input' -> input'
+    l = case runParser parseDigitReversed "parseDigit" (reverse str) of
+      Left bundle -> error $ errorBundlePretty bundle
+      Right input' -> input'
+
+parseInput' :: Parser Input
+parseInput' = fmap parseFirstAndLast <$> some (some alphaNumChar <* eol) <* eof
+
+parseInput :: String -> IO Input
+parseInput filename = do
+  input <- readFile filename
+  case runParser parseInput' filename input of
+    Left bundle -> error $ errorBundlePretty bundle
+    Right input' -> return input'
+
+process :: Int -> (Int, Int) -> Int
+process acc l = acc + fst l * 10 + snd l
+
+compute :: Input -> Int
+compute = L.foldl' process 0
+
+main :: IO ()
+main = do
+  example <- parseInput "example2"
+  let exampleOutput = compute example
+  when  (exampleOutput /= exampleExpectedOutput)  (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
+  input <- parseInput "input"
+  print $ compute input