9th day

app/9.hs

@@ -2,10 +2,7 @@
 module Main where
 
 import Data.Functor
-import Data.List
-import Data.List.Split
 import Data.List.Extra hiding (split)
-import Debug.Trace
 
 data ℜ where
   None :: ℜ
@@ -34,18 +31,18 @@ fit :: [[ℜ]] -> [ℜ] -> [ℜ]
 fit s t = let (p,a) = break (elem None) s
               (n,a') = span (elem None) a in
             if null n then concat s ++ t else
-  concat p ++ if length (head n) >= length t then t ++ replicate (length n) None ++ concat a' else concat n ++ fit a' t
+  concat p ++ if length (head n) >= length t then t ++ replicate (length (head n) - length t) None ++ concat a' ++ replicate (length t) None else concat n ++ fit a' t
 
 sort2 :: [ℜ] -> [ℜ]
-sort2 s = let c = chunks s in
-            if notElem None $ last c
-            then let fitted = fit (init c) (last c) in
-                if s == fitted then head c ++ case c of
-                  [] -> []
-                  [c] -> c
-                  c@[_,_] -> concat c
-                  c -> sort2 (concat . tail $ init c) ++ last c else sort2 fitted
-            else sort2 (concat $ init c) ++ last c
+sort2 s = let c = chunks s
+              fitted = fit (init c) (last c)
+              c' = chunks fitted
+          in
+          case length c' of
+            0 -> concat c'
+            1 -> concat c'
+            2 -> concat c'
+            _ -> (sort2 . concat $ init c') ++ last c'
 
 solve :: ([ℜ] -> [ℜ]) -> [ℜ] -> Int
 solve f s = let fixed = (\case
@@ -54,6 +51,6 @@ solve f s = let fixed = (\case
   sum $ zipWith (*) fixed [0..]
 
 main :: IO ()
-main = readFile "inputs/9.example" <&> parse >>= \i ->
+main = readFile "inputs/9" <&> parse >>= \i ->
        print (solve sort1 i) >>
        print (solve sort2 i)