1 files changed, 40 insertions, 0 deletions
diff --git a/2020/2.hs b/2020/2.hs
new file mode 100644
index 0000000..7b83745
--- /dev/null
+++ b/2020/2.hs
@@ -0,0 +1,40 @@
+module Main where
+
+import Text.Parsec (parse, digit, char, string, anyChar, many, many1)
+
+import Input
+
+
+data Policy = Policy Int Int Char
+  deriving (Show)
+
+parseLine :: String -> (Policy, String)
+parseLine str = case parse pLine "" str of Right r -> r ; Left e -> error (show e)
+  where
+    pLine = do
+        n1 <- read <$> many1 digit
+        _ <- char '-'
+        n2 <- read <$> many1 digit
+        _ <- char ' '
+        c <- anyChar
+        _ <- string ": "
+        s <- many anyChar
+        return (Policy n1 n2 c, s)
+
+valid1 :: Policy -> String -> Bool
+valid1 (Policy l h c) pw =
+    let count = length (filter (== c) pw)
+    in l <= count && count <= h
+
+valid2 :: Policy -> String -> Bool
+valid2 (Policy l h c) pw =
+    let c1 = pw !! (l - 1) ; c2 = pw !! (h - 1) in (c1 == c || c2 == c) && c1 /= c2
+
+numValid :: (Policy -> String -> Bool) -> [(Policy, String)] -> Int
+numValid f = sum . map (fromEnum . uncurry f)
+
+main :: IO ()
+main = do
+    input <- map parseLine <$> getInput 2
+    print (numValid valid1 input)
+    print (numValid valid2 input)