add initial day 2 solution

1 files changed, 39 insertions, 0 deletions

diff --git a/execs/Day02.hs b/execs/Day02.hs
new file mode 100644
index 0000000..bcb0896
--- /dev/null
+++ b/execs/Day02.hs
@@ -0,0 +1,39 @@
+module Main where
+
+import Data.Char
+import Control.Monad
+
+countElem :: (Eq a) => a -> [a] -> Int
+countElem c ls = sum $ map (fromEnum . (== c)) ls
+
+xor :: Bool -> Bool -> Bool
+xor True True   = False
+xor True False  = True
+xor False True  = True
+xor False False = False
+
+ranges :: [String] -> (Int, Int)
+ranges r =
+    let p = head r
+        start = read $ takeWhile (/= '-') p
+        end = abs . read $ dropWhile (/= '-') p
+     in (start, end)
+
+charac :: [String] -> Char
+charac s = head (s !! 1)
+
+pass :: [String] -> String
+pass = last
+
+doCheck1 :: ((Int, Int), Char , String) -> Bool
+doCheck1 ((lower, upper), c, pass) = count >= lower && count <= upper
+    where count = countElem c pass
+
+doCheck2 :: ((Int, Int), Char , String) -> Bool
+doCheck2 ((lower, upper), c, pass) = (pass !! (lower - 1) == c) `xor` (pass !! (upper - 1) == c)
+
+main :: IO ()
+main = do
+    n <- map (fromEnum . doCheck2 . (\w -> (ranges w, charac w, pass w)) . words) . lines <$> readFile "input/02"
+    print $ sum n
+