add initial day 3 solution

2 files changed, 18 insertions, 4 deletions

diff --git a/execs/Day02.hs b/execs/Day02.hs
index 87c90ec..f67778b 100644
--- a/execs/Day02.hs
+++ b/execs/Day02.hs
@@ -1,8 +1,5 @@
 module Main where
 
-import Data.Char
-import Data.Either
-import Control.Monad
 import Text.ParserCombinators.Parsec
 import Text.Parsec.Char
 
@@ -42,4 +39,3 @@ main :: IO ()
 main = do
     n <- map (fromEnum . doCheck2 . parseLine parseProp) . lines <$> readFile "input/02"
     print $ sum n
-
diff --git a/execs/Day03.hs b/execs/Day03.hs
new file mode 100644
index 0000000..a000e59
--- /dev/null
+++ b/execs/Day03.hs
@@ -0,0 +1,18 @@
+module Main where
+
+main :: IO ()
+main = do
+    n <- lines <$> readFile "input/03"
+    print $ countTrees 3 1 n
+    print $ product [ countTrees 1 1 n
+                    , countTrees 3 1 n
+                    , countTrees 5 1 n
+                    , countTrees 7 1 n
+                    , countTrees 1 2 n
+                    ]
+
+countTrees :: Int -> Int -> [String] -> Int
+countTrees right down ls = go (map cycle ls)
+    where go [] = 0
+          go remaining@(r:rs) = i (head r) + go (map (drop right) (drop down remaining))
+              where i = fromEnum . (== '#')