day15: not working

to be discarded, but cool enough to keep around in git I guess

2023/day15/day15.hs

@@ -1,16 +1,14 @@
-{-# LANGUAGE LambdaCase #-}
-
-import Debug.Trace
-import Data.List
-import Text.Read
 import Control.Arrow
+import Data.Function
+import Data.List
 import Data.List.Split
-import qualified Data.Map as M
+import Data.Maybe
+import Text.Read
 
 type HASH = (String, Maybe Int)
 
 main :: IO ()
-main = interact $ show . parse . init
+main = interact $ show . genBuckets . parse . init
 
 parse :: String -> [HASH]
 parse = map (second (readMaybe . tail) . break (`elem` "=-")) . splitOn ","
@@ -21,12 +19,25 @@ day15a = sum . map (foldl' hashAlg 0) . splitOn ","
 hashAlg :: Int -> Char -> Int
 hashAlg x y = (17 * (fromEnum y + x)) `mod` 256
 
-removeHash :: [HASH] -> HASH -> [HASH]
-removeHash hs (s,n) = undefined
+removeHashes :: [String] -> [HASH] -> [HASH]
+removeHashes _ [] = []
+removeHashes rs ((label, Nothing):xs) = removeHashes (label : rs) xs
+removeHashes rs ((label, Just x):xs)
+  | label `elem` rs = removeHashes (delete label rs) xs
+  | otherwise = (label, Just x) : removeHashes rs xs
 
-
-f1 n (x,_) = foldl hashAlg 0 x == n
-f2 s (x,_) = x==s
-
-
--- input <- lines <$> readFile "testinput"
+genBuckets :: [HASH] -> Int
+genBuckets input =
+  sum
+    [ sum $ zipWith (*) [1 ..] $ map ((* (succ x)) . fromJust . snd) (sorted x)
+    | x <- [0 .. 255]
+    ]
+  where
+    filterBucket x f =
+      nubBy ((==) `on` fst) $
+      f $ removeHashes [] (reverse $ filter (f1 x) input)
+    sorted x =
+      sortOn
+        (\y -> fst y `elemIndex` (map fst (filterBucket x reverse)))
+        (filterBucket x id)
+    f1 n (x, _) = foldl hashAlg 0 x == n