1 files changed, 53 insertions, 0 deletions
diff --git a/src/Day2.idr b/src/Day2.idr
new file mode 100644
index 0000000..c3b26aa
--- /dev/null
+++ b/src/Day2.idr
@@ -0,0 +1,53 @@
+module Day2
+
+import Data.String
+
+
+parseRow : String -> List Int
+parseRow str = do
+  num <- words str
+  maybe [] pure (parseInteger num)
+
+parseInp : String -> List (List Int)
+parseInp inp = do
+  numrow <- lines inp
+  pure $ parseRow numrow
+  
+isSafe : List Int -> Bool
+isSafe [] = False
+isSafe (x :: xs) = fst up || fst down where
+  up   = foldl (\(b, y) => \n => (b && y - n <= 3 && y - n > 0, n)) (True, x) xs
+  down = foldl (\(b, y) => \n => (b && n - y <= 3 && n - y > 0, n)) (True, x) xs
+
+btoi : Bool -> Int
+btoi False = 0
+btoi True = 1
+
+part1 : List (List Int) -> Int
+part1 iss = sum $ map (btoi . isSafe) iss
+
+export sol1 : String -> String
+sol1 = show . part1 . parseInp
+
+upCheck, downCheck : Int -> Int -> Bool
+upCheck   i j = i - j <= 3 && i - j > 0
+downCheck i j = j - i <= 3 && j - i > 0
+
+safeTerm : (Int -> Int -> Bool) -> (Bool, Bool, Int) -> Int -> (Bool, Bool, Int)
+safeTerm f (False, (y, z)) i = (False, y, i)
+safeTerm f (True, (False, z)) i = (f z i, False, i)
+safeTerm f (True, (True, z)) i = if f z i then (True, True, i) else (True, False, z)
+
+isSafe' : Bool -> List Int -> Bool
+isSafe' b [] = False
+isSafe' b (x :: []) = True
+isSafe' b (x :: (y :: xs)) = isSafe (x :: y :: xs) || (b && isSafe' False (y :: xs)) || (b && isSafe' False (x :: xs))
+
+part2 : List (List Int) -> Int
+part2 iss = sum $ map (btoi . isSafe' True) iss
+
+export sol2 : String -> String
+sol2 = show . part2 . parseInp
+
+export out : String -> String
+out = show . parseInp