day3

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

day3.hs

@@ -0,0 +1,31 @@
+import Data.Char (isAsciiLower, isAsciiUpper)
+import Data.List (intersect)
+import Lib (chunks)
+
+-- we do not use a simple 9 value case cuz yeah
+
+main :: IO ()
+main = do
+  input <- readFile "day3.in"
+  putStr "Q1: "
+  print $ q1 input
+  putStr "Q2: "
+  print $ q2 input
+
+q1 :: String -> Int
+q1 =
+  sum
+    . map (\x -> val . head . uncurry intersect $ splitAt (div (length x) 2) x)
+    . lines
+
+q2 =
+  sum
+    . map (val . head . foldr1 intersect)
+    . chunks 3
+    . lines
+
+val :: Char -> Int
+val c
+  | isAsciiLower c = 1 + fromEnum c - fromEnum 'a'
+  | isAsciiUpper c = 27 + fromEnum c - fromEnum 'A'
+  | otherwise = 0