X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=adventofcode16%2Fapp%2Fadvent04.hs;fp=adventofcode16%2Fapp%2Fadvent04.hs;h=85b75552678ec85137db5b479dca8450e0e6610b;hb=fd498a2713d69a5d55179ff07e58ce296d6fba94;hp=0000000000000000000000000000000000000000;hpb=3a26b187d5dc23b05fb73daabe52a92976a7a3c7;p=advent-of-code-16.git

diff --git a/adventofcode16/app/advent04.hs b/adventofcode16/app/advent04.hs
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+++ b/adventofcode16/app/advent04.hs
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+module Main(main) where
+
+import Data.List (last, intersperse, sortBy, intercalate, isInfixOf, init)
+import Data.List.Split (splitOn)
+import Data.Char (isLetter, ord, chr)
+import qualified Data.Map.Lazy as Map
+
+data Room = Room { name :: String
+                 , sector :: Int
+                 , checksum :: String
+                 } deriving (Show)
+
+main :: IO ()
+main = do 
+        instrText <- readFile "data/advent04.txt" 
+        let rooms = map (parseLine) $ lines instrText
+        part1 rooms
+        part2 rooms
+
+
+part1 :: [Room] -> IO ()
+part1 rooms = do 
+    print $ sum $ map (sector) validRooms
+    where 
+        validChecksum room = (checksum room) == makeChecksum (name room)
+        validRooms = filter (validChecksum) rooms
+
+part2 :: [Room] -> IO ()
+part2 rooms = do 
+    print $ fst $ head $ filter (\sn -> isInfixOf "north" (snd sn)) sectorNames
+    where 
+        validChecksum room = (checksum room) == makeChecksum (name room)
+        validRooms = filter (validChecksum) rooms
+        sectorNames = [((sector r),
+            shiftWord (sector r) (name r)) | r <- validRooms]
+
+
+parseLine :: String -> Room
+parseLine line = Room {name=name, sector=sector, checksum=checksum}
+    where components = splitOn "-" line
+          name = intercalate "-" $ init components
+          sector = read $ head $ splitOn "[" $ last components
+          checksum = filter (isLetter) $ last components
+
+countedLetters :: String -> [(Char, Int)]
+countedLetters name = sortBy sortCLetter $ unsortedCountedLetters name
+    where unsortedCountedLetters name = 
+            Map.toList $ Map.fromListWith (+) [(c, 1) | c <- filter (isLetter) name]
+
+sortCLetter :: (Char, Int) -> (Char, Int) -> Ordering
+sortCLetter (l1, n1) (l2, n2)
+    | n1 < n2 = GT
+    | n1 > n2 = LT
+    | n1 == n2 = compare l1 l2
+
+makeChecksum :: String -> String
+makeChecksum name = [l | (l, _) <- take 5 $ countedLetters name]
+
+
+shiftWord :: Int -> String -> String
+shiftWord shift letters = map (shiftLetter shift) letters
+
+shiftLetter :: Int -> Char -> Char
+shiftLetter shift letter
+    | isLetter letter = chr $ (ord letter - ord 'a' + shift) `mod` 26 + ord 'a'
+    | otherwise = ' '