Day 6 Part 2

06/Main.idr

@@ -13,30 +13,44 @@ windows {n} xs =
       Nothing => []
       (Just x) => x :: windows tail
 
-findStartOfPacket : List Char -> Maybe Nat
-findStartOfPacket cs =
-  let segments = windows {n = 4} cs
-  in case findIndex (\x => let ( p ** _ ) = nub x in p == 4) segments of
+findStart : Nat -> List Char -> Maybe Nat
+findStart n cs =
+  let segments = windows {n} cs
+  in case findIndex (\x => let ( p ** _ ) = nub x in p == n) segments of
        Nothing => Nothing
-       (Just x) => Just $ finToNat x + 4
+       (Just x) => Just $ finToNat x + n
 
-testCases : List (String, Nat)
-testCases = [("mjqjpqmgbljsphdztnvjfqwrcgsmlb", 7),
-             ("bvwbjplbgvbhsrlpgdmjqwftvncz",5),
-             ("nppdvjthqldpwncqszvftbrmjlhg",6),
-             ("nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg",10),
-             ("zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw",11)]
+findStartOfPacket : List Char -> Maybe Nat
+findStartOfPacket = findStart 4
 
-testCase : (String, Nat) -> IO Bool
-testCase (string, start) =
+findStartOfMessage : List Char -> Maybe Nat
+findStartOfMessage = findStart 14
+
+testCases : List (String, Nat, Nat)
+testCases = [("mjqjpqmgbljsphdztnvjfqwrcgsmlb", 7, 19),
+             ("bvwbjplbgvbhsrlpgdmjqwftvncz", 5, 23),
+             ("nppdvjthqldpwncqszvftbrmjlhg", 6, 23),
+             ("nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg", 10, 29),
+             ("zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw", 11, 26)]
+
+testCase : (String, Nat, Nat) -> IO Bool
+testCase (string, start, message) =
   do putStrLn $ "Test Case: " ++ string
-     putStrLn $ "Expected Start: " ++ show start
+     putStrLn $ "Expected Start of packet: " ++ show start
+     putStrLn $ "Expected Start of message: " ++ show message
      let result = findStartOfPacket (unpack string)
-     putStrLn $ "Evaluated start: " ++ show result
+     let messageResult = findStartOfMessage (unpack string)
+     putStrLn $ "Evaluated start of packet: " ++ show result
+     putStrLn $ "Evaluated start of message: " ++ show messageResult
      let result = not (result == Just start)
-     if result
-       then putStrLn "Test Failed!!!"
-       else putStrLn "Test Passed"
+     result <- if result
+               then do putStrLn "Test Failed!!!"
+                       pure True
+               else if messageResult == Just message
+                      then do putStrLn "Test Passed"
+                              pure False
+                      else do putStrLn "Test Failed!!!"
+                              pure True
      putStrLn ""
      pure result
 
@@ -53,4 +67,9 @@ main =
                    putStrLn $ case findStartOfPacket (unpack contents) of
                                Just start => show start
                                Nothing => "Failed to find start"
+                   putStr "Part 2: "
+                   putStrLn $ case findStartOfMessage (unpack contents) of
+                               Just start => show start
+                               Nothing => "Failed to find start"
+
               Left err => printLn err