Day 8 done

[advent-of-code-19.git] / advent08 / src / advent08.hs

diff --git a/advent08/src/advent08.hs b/advent08/src/advent08.hs
new file mode 100644 (file)
index 0000000..fe00af5
--- /dev/null
+++ b/advent08/src/advent08.hs
@@ -0,0 +1,49 @@
+import Data.List
+import Data.List.Split
+import Data.Char
+import Data.Ord
+import Data.Function
+
+main :: IO ()
+main = do 
+        text <- readFile "data/advent08.txt"
+        let digits = successfulParse text
+        let layers = chunksOf (imageWidth * imageHeight) digits
+        print $ part1 layers
+        putStrLn $ part2 layers
+
+
+imageWidth = 25
+imageHeight = 6
+
+part1 layers = (count 1 target) * (count 2 target)
+    where target = minimumBy (comparing (count 0)) layers
+
+part2 layers = unlines rows
+    where pixelLayers = transpose layers
+          pixels = map firstVisible pixelLayers
+          dPixels = map showPixel pixels
+          pixelRows = chunksOf imageWidth dPixels
+          rows = map concat pixelRows
+
+
+firstVisible = head . dropWhile (== 2)
+
+showPixel 0 = " "
+showPixel 1 = "\x2588"
+
+
+count n = length . filter (== n)
+
+-- Count the number of times a predicate is true
+-- (Taken from GHC API utility functions)
+
+-- count :: (a -> Bool) -> [a] -> Int
+-- count p = go 0
+--   where go !n [] = n
+--         go !n (x:xs) | p x       = go (n+1) xs
+--                      | otherwise = go n xs
+
+
+successfulParse :: String -> [Int]
+successfulParse input = map digitToInt input
\ No newline at end of file