Day 13 Part 2

13/Main.idr

@@ -25,6 +25,26 @@ Show Data where
     let inner = joinBy "," . toList . map (\x => show (assert_smaller input x)) $ contents in
     "[" ++ inner ++ "]"
 
+Eq Data where
+  (==) (MkAtom atom) (MkAtom k) = atom == k
+  (==) (MkAtom atom) (MkList n contents) = False
+  (==) (MkList n contents) (MkAtom atom) = False
+  (==) (MkList n contents) (MkList k xs) = helper (toList contents) (toList xs)
+    where helper : List Data -> List Data -> Bool
+          helper [] [] = True
+          helper (x :: xs) [] = False
+          helper [] (x :: xs) = False
+          helper ((MkAtom atom) :: xs) ((MkAtom j) :: ys) =
+            if atom == j
+              then helper xs ys
+              else False
+          helper ((MkAtom atom) :: xs) ((MkList j zs) :: ys) = False
+          helper ((MkList j zs) :: xs) ((MkAtom atom) :: ys) = False
+          helper input1@((MkList j zs) :: xs) ((MkList i ws) :: ys) =
+            if helper (assert_smaller input1 (toList zs)) (toList ws)
+              then helper xs ys
+              else False
+
 atomToList : Nat -> Data
 atomToList i = MkList 1 [MkAtom i]
 
@@ -122,46 +142,13 @@ parsePairs str =
              y <- parseData y
              pure (x, y)
 
-simple = """
-  [1,1,3,1,1]
-  [1,1,5,1,1]
-
-  [[1],[2,3,4]]
-  [[1],4]
-
-  [9]
-  [[8,7,6]]
-
-  [[4,4],4,4]
-  [[4,4],4,4,4]
-
-  [7,7,7,7]
-  [7,7,7]
-
-  []
-  [3]
-
-  [[[]]]
-  [[]]
-
-  [1,[2,[3,[4,[5,6,7]]]],8,9]
-  [1,[2,[3,[4,[5,6,0]]]],8,9]
-  """
-
-testPart1 : IO ()
-testPart1 =
-  do Just (n ** pairs) <- pure (parsePairs simple)
-       | Nothing => putStrLn "Failed to parse pairs"
-     let indicies = allFins' n
-     let correct_order =
-       map S .
-       map finToNat .
-       filter (\x =>
-                let (x,y) = index x pairs
-                in checkOrder x y) $
-       indicies
-     printLn pairs
-     printLn correct_order
+parseVect : String -> Maybe (m : Nat ** Vect m Data)
+parseVect str =
+  do let lines = filter (not . (=="")). map trim . lines $ str
+     datas <- traverse parseData lines
+     let m = length datas
+     datas <- toVect m datas
+     pure (m ** datas)
 
 part1 : (pairs : (n : Nat ** Vect n (Data, Data))) -> Nat
 part1 (n ** pairs) =
@@ -175,6 +162,26 @@ part1 (n ** pairs) =
         indicies
   in sum correct_order
 
+sort : {n : Nat} -> Vect n Data -> Vect n Data
+sort [] = []
+sort (x :: xs) = insert x (sort xs)
+  where insert : {m : Nat} -> Data -> Vect m Data -> Vect (S m) Data
+        insert x [] = [x]
+        insert x rest@(y :: xs) =
+          if checkOrder x y
+            then x :: y :: xs
+            else y :: insert x xs
+
+part2 : (datas : (m : Nat ** Vect m Data)) -> Maybe Nat
+part2 (m ** datas) =
+  do let divider_packets =
+           (MkList 1 [MkList 1 [MkAtom 2]]) :: (MkList 1 [MkList 1 [MkAtom 6]]) :: datas
+     let sorted = sort divider_packets
+     divider_1 <- findIndex (== MkList 1 [MkList 1 [MkAtom 2]]) sorted
+     divider_2 <- findIndex (== MkList 1 [MkList 1 [MkAtom 6]]) sorted
+     let (divider_1, divider_2) = (1 + finToNat divider_1, 1 + finToNat divider_2)
+     pure (divider_1 * divider_2)
+
 main : IO ()
 main =
   do Right file <- readFile "input"
@@ -182,3 +189,8 @@ main =
      Just pairs <- pure (parsePairs file)
        | Nothing => putStrLn "Failed parsing input"
      putStrLn $ "Part 1: " ++ show (part1 pairs)
+     Just datas <- pure (parseVect file)
+       | Nothing => putStrLn "Failed parsing input"
+     Just part2Result <- pure (part2 datas)
+       | Nothing => putStrLn "Error in part2"
+     putStrLn $ "Part 2: " ++ show part2Result