Day 6

.editorconfig

@@ -4,3 +4,7 @@ root = true
 end_of_line = lf
 insert_final_newline = false
 trim_trailing_whitespace = true
+
+[*.hs]
+indent_size = 2
+indent_style = space

day6/eg.txt

@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200

day6/input.txt

@@ -0,0 +1,2 @@
+Time:        56     71     79     99
+Distance:   334   1135   1350   2430

day6/main.hs

@@ -0,0 +1,38 @@
+type Race = (Int, Int)
+
+loadRaces :: String -> [Race]
+loadRaces str = zip ts ds
+  where
+    [ts, ds] = map getNs $ splitStr '\n' str
+    getNs :: String -> [Int]
+    getNs = map read . filter (not . null) . splitStr ' ' . drop 2 . dropWhile (/=':')
+
+loadRace :: String -> Race
+loadRace str = (t, d)
+  where
+    [t, d] = map getN $ splitStr '\n' str
+    getN :: String -> Int
+    getN = read . filter (/= ' ') . drop 2 . dropWhile (/= ':')
+
+splitStr :: Char -> String -> [String]
+splitStr onC = foldr splitStr' [""]
+  where
+    splitStr' :: Char -> [String] -> [String]
+    splitStr' c (cur:splits)
+      | c == onC  = "":cur:splits
+      | otherwise = (c:cur):splits
+
+raceOptions :: Race -> Int
+raceOptions (t, d) = t + 1 - 2 * head [n | n <- [0..t], n * (t-n) > d]
+
+part1 :: String -> String
+part1 = show . product . map raceOptions . loadRaces
+
+part2 :: String -> String
+part2 = show . raceOptions . loadRace
+
+main :: IO ()
+main = do
+  s <- readFile "input.txt"
+  putStrLn $ "Part 1: " ++ part1 s
+  putStrLn $ "Part 2: " ++ part2 s