solve: day 6, part 2 - bitwise

2020/06/part2_bits.hs

@@ -0,0 +1,17 @@
+#!/usr/bin/env runghc
+
+
+import Day6
+import Data.Bits
+import Data.Char
+
+main = interact (show . solve . lines')
+
+solve = sum . map countEveryoneYes
+
+charToBit c = bit $ ord c - ord 'a'
+
+stringToBits :: String -> Int
+stringToBits str = foldl1 (.|.) $ map charToBit str
+
+countEveryoneYes group = popCount $ foldl1 (.&.) $ map stringToBits group