Alternative, using an interval library

diff --git a/advent-of-code22.cabal b/advent-of-code22.cabal
index a374b428786c5fe6c5cec13f94d466380081d397..ca418749b82df36bb26e4a190b41eedc89dcc372 100644 (file)
--- a/advent-of-code22.cabal
+++ b/advent-of-code22.cabal
@@ -108,4 +108,9 @@ executable advent03
 executable advent04
   import: common-extensions, build-directives
   main-is: advent04/Main.hs
-  build-depends: text, attoparsec
\ No newline at end of file
+  build-depends: text, attoparsec
+
+executable advent04i
+  import: common-extensions, build-directives
+  main-is: advent04/Main-interval.hs
+  build-depends: text, attoparsec, intervals

diff --git a/advent04/Main-interval.hs b/advent04/Main-interval.hs
new file mode 100644 (file)
index 0000000..7888fae
--- /dev/null
+++ b/advent04/Main-interval.hs
@@ -0,0 +1,57 @@
+-- Writeup at https://work.njae.me.uk/2022/12/04/advent-of-code-2022-day-4/
+
+import System.Environment
+import Data.Text (Text)
+import qualified Data.Text.IO as TIO
+import Data.Attoparsec.Text hiding (Result)
+import Numeric.Interval hiding (null)
+-- import Control.Applicative
+
+type Assignment = Interval Int
+type Pair = (Assignment, Assignment)
+
+main :: IO ()
+main = 
+  do  dataFileName <- getDataFileName
+      text <- TIO.readFile dataFileName
+      let pairs = successfulParse text
+      print $ part1 pairs
+      print $ part2 pairs
+
+getDataFileName :: IO String
+getDataFileName =
+  do args <- getArgs
+     progName <- getProgName
+     let baseDataName =  if null args
+                         then progName
+                         else head args 
+     let dataFileName = "data/" ++ baseDataName ++ ".txt"
+     return dataFileName
+
+part1 :: [Pair] -> Int
+part1 = length . (filter hasContainment)
+
+part2 :: [Pair] -> Int
+part2 = length . (filter $ uncurry (==?))
+
+hasContainment :: Pair -> Bool
+hasContainment (assignment1, assignment2) = 
+  (assignment1 `contains` assignment2) || (assignment2 `contains` assignment1)
+
+
+-- Parse the input file
+
+pairsP :: Parser [Pair]
+pairP :: Parser Pair
+assignmentP :: Parser Assignment
+
+pairsP = pairP `sepBy` endOfLine
+pairP = (,) <$> assignmentP <* "," <*> assignmentP
+
+assignmentP = (...) <$> decimal <* "-" <*> decimal
+
+successfulParse :: Text -> [Pair]
+successfulParse input = 
+  case parseOnly pairsP input of
+    Left  _err -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
+    Right pairs -> pairs