From e0632dd35e0dd6491397514d09ad273f4d1e0392 Mon Sep 17 00:00:00 2001 From: Tom Smeding Date: Fri, 3 Dec 2021 20:28:40 +0100 Subject: 3 --- 2021/3.hs | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) create mode 100644 2021/3.hs (limited to '2021/3.hs') diff --git a/2021/3.hs b/2021/3.hs new file mode 100644 index 0000000..98ca15c --- /dev/null +++ b/2021/3.hs @@ -0,0 +1,25 @@ +module Main where + +import Data.Bits +import Data.List + +import Input + + +readBin :: [Bool] -> Int +readBin = sum . zipWith (*) (iterate (*2) 1) . reverse . map fromEnum + +main :: IO () +main = do + inp <- map (map (== '1')) <$> getInput 3 + let n = length (head inp) + let majority s = 2 * length (filter id s) > length s + let gamma = readBin $ map majority $ transpose inp + epsilon = complement gamma .&. (bit n - 1) + print (gamma * epsilon) + let filterstep _ _ [x] = [x] + filterstep target idx cands = filter ((== target) . (!! idx)) cands + perform targetrule = foldl' (\cs i -> filterstep (targetrule cs i) i cs) inp [0 .. n - 1] + oxygen = perform $ \cs i -> 2 * length (filter id (map (!! i) cs)) >= length cs + co2 = perform $ \cs i -> 2 * length (filter id (map (!! i) cs)) < length cs + print (readBin (head oxygen) * readBin (head co2)) -- cgit v1.2.3-54-g00ecf