Finished day 6

src/Day5Lib.hs

@@ -1,4 +1,7 @@
-module Day5Lib where
+module Day5Lib
+    ( day5,
+      day5Alternate
+    ) where
 
 import Data.List (transpose)
 import Data.List.Split

src/Day6Lib.hs

@@ -0,0 +1,49 @@
+module Day6Lib where
+    -- ( day6,
+    --   day6'
+    -- ) where
+
+import Data.List (nub, elemIndex)
+import Data.Maybe (fromJust)
+
+-- Using windows of 4 characters to solve this problem
+type Window = [Char]
+
+-- For start of packet markers
+splitStringIntoWindows :: String -> [Window]
+splitStringIntoWindows "" = []
+splitStringIntoWindows (a:[]) = []
+splitStringIntoWindows (a:b:[]) = []
+splitStringIntoWindows (a:b:c:[]) = []
+splitStringIntoWindows (a:b:c:d:[]) = [[a,b,c,d]]
+splitStringIntoWindows string@(a:b:c:d:rest) = [a,b,c,d] : (splitStringIntoWindows $ tail string)
+
+-- For start of message markers
+-- This is non-exhaustive but there is no need to write all this out :/
+splitStringIntoWindows' :: String -> [Window]
+splitStringIntoWindows' "" = []
+splitStringIntoWindows' (a:b:c:d:e:f:g:h:i:j:k:l:m:n:[]) = [[a,b,c,d,e,f,g,h,i,j,k,l,m,n]]
+splitStringIntoWindows' string@(a:b:c:d:e:f:g:h:i:j:k:l:m:n:rest) =
+    [a,b,c,d,e,f,g,h,i,j,k,l,m,n] : (splitStringIntoWindows' $ tail string)
+
+-- Use the nub function to eliminate duplicate elements and check lenght before/after
+findAllUniqueWindow :: Window -> Bool
+findAllUniqueWindow w = (length w) == (length $ nub w)
+
+day6 :: String -> Int
+day6 input = indexAdjustedForOffset
+    where
+        windows = splitStringIntoWindows input
+        uniqueWindows = filter findAllUniqueWindow windows
+        firstUniqueWindow = head uniqueWindows
+        index = fromJust $ elemIndex firstUniqueWindow windows
+        indexAdjustedForOffset = index + 4
+
+day6' :: String -> Int
+day6' input = indexAdjustedForOffset
+    where
+        windows = splitStringIntoWindows' input
+        uniqueWindows = filter findAllUniqueWindow windows
+        firstUniqueWindow = head uniqueWindows
+        index = fromJust $ elemIndex firstUniqueWindow windows
+        indexAdjustedForOffset = index + 14