Day 6

day06/Commons.hs

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+module Commons where
+
+import Data.List.Utils (split)
+
+
+data Race = Race { time :: Int, distance :: Int } deriving Show
+
+
+parseRaces :: [Int] -> [Int] -> [Race]
+parseRaces (th: tt) (dh: dt) = Race {time = th, distance = dh}: parseRaces tt dt
+parseRaces [] [] = []
+
+parseTimes :: [String] -> [Int]
+parseTimes (('T': _): t) = parseTimes t
+parseTimes ([]: t) = parseTimes t
+parseTimes (h: t) = read h: parseTimes t
+parseTimes [] = []
+
+parseDistances :: [String] -> [Int]
+parseDistances (('D': _): t) = parseDistances t
+parseDistances ([]: t) = parseDistances t
+parseDistances (h: t) = read h: parseDistances t
+parseDistances [] = []
+
+parse :: IO [Race]
+parse = do rawTimes <- getLine
+           let times = parseTimes $ split " " rawTimes
+           rawDistances <- getLine
+           let distances = parseDistances $ split " " rawDistances
+           return $ parseRaces times distances
+
+
+getDistance :: Int -> Int -> Int
+getDistance holdTime totalTime = (totalTime - holdTime) * holdTime
+
+getMinimalHoldTime :: Race -> Int -> Int
+getMinimalHoldTime race holdTime | getDistance holdTime (time race) > distance race = holdTime
+                                 | otherwise = getMinimalHoldTime race (holdTime + 1)
+
+getRaceRange :: Race -> Int
+getRaceRange race = time race + 1 - 2 * getMinimalHoldTime race 0

day06/Main.hs

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+module Main where
+
+import Commons
+import qualified Part1
+import qualified Part2
+
+
+main = do races <- parse
+          let part1Res = product $ Part1.getRanges races
+          print part1Res
+          let part2Res = Part2.getRange races
+          print part2Res

day06/Part1.hs

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+module Part1 where
+
+import Commons
+
+
+getRanges :: [Race] -> [Int]
+getRanges = map getRaceRange

day06/Part2.hs

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+module Part2 where
+
+import Commons
+
+
+getSingleRace :: [Race] -> Race
+getSingleRace [race] = race
+getSingleRace (rh: t) = let otherRace = getSingleRace t
+                        in Race {time = read $ show (time rh) ++ show (time otherRace),
+                                 distance = read $ show (distance rh) ++ show (distance otherRace)}
+
+getRange :: [Race] -> Int
+getRange = getRaceRange . getSingleRace