Solve day 1 part 2

app/Main.hs

@@ -1,6 +1,7 @@
 module Main (main) where
 
 import Control.Monad.State
+import Data.Bifunctor
 import Data.Traversable
 import Text.Read (readMaybe)
 
@@ -19,8 +20,21 @@ main = do
         . sum
         . flip evalState 50
         $ for input \(d, i) -> state \p ->
-            let p' = step i d p
+            let (_, p') = step i d p
              in (Count if p' == 0 then 1 else 0, p')
+    print
+        . sum
+        . flip evalState 50
+        $ for input \(d, i) -> state \p ->
+            let (c, p') = step i d p
+                c' = case d of
+                    R -> abs c
+                    L ->
+                        if
+                            | p == 0 -> abs c - 1
+                            | p' == 0 -> abs c + 1
+                            | otherwise -> abs c
+             in (c', p')
 
 data Direction = L | R
     deriving (Eq, Ord, Show)
@@ -34,7 +48,7 @@ newtype Inc = Inc Int
 newtype Count = Count Int
     deriving newtype (Eq, Ord, Show, Num)
 
-step :: Inc -> Direction -> Pos -> Pos
-step (Inc i) d (Pos p) = Pos case d of
-    L -> (p - i) `mod` 100
-    R -> (p + i) `mod` 100
+step :: Inc -> Direction -> Pos -> (Count, Pos)
+step (Inc i) d (Pos p) = bimap Count Pos case d of
+    L -> (p - i) `divMod` 100
+    R -> (p + i) `divMod` 100