Day 07 - part 2.

README.md

@@ -14,7 +14,7 @@ To arrive at [⟨ortho|normal⟩](https://hilb.ert.space) as December comes.
 | 04  | ~ 1         |
 | 05  | ~ 1         |
 | 06  | ~ 3         |
-| 07  |             |
+| 07  | ~ 1         |
 | 08  |             |
 | 09  |             |
 | 10  |             |

src/Day07.hs

@@ -1,28 +1,56 @@
 module Day07 (main) where
 
-import Data.Map (Map, fromListWith, fromList, findMin)
-import qualified Data.Map as M (union, null, filter, delete)
-import Data.Set (Set, singleton, empty)
-import qualified Data.Set as S (union, null, delete)
+import Data.List (partition)
+import Data.Map (Map, fromListWith, fromList, findMin, findMax)
+import qualified Data.Map as M (union, null, delete, empty, filter)
+import Data.Set (Set, singleton)
+import qualified Data.Set as S (union, null, delete, empty)
 import Data.Tuple.Extra (second)
 
+-- Deps = Task => Dependencies
+type Deps = Map Char (Set Char)
+
+-- Worker = (Task, Time)
+type Worker = (Char, Int)
+emptyWorker = (' ', 0)
+
 parse :: String -> (Char, Char)
 parse str = (str !! 36, str !! 5)
 
-dependencies :: [(Char, Char)] -> Map Char (Set Char)
+dependencies :: [(Char, Char)] -> Deps
 dependencies ds =
     let dependents   = fromListWith S.union . map (second singleton) $ ds
-        independents = fromList . (flip zip) (repeat empty) . snd . unzip $ ds
+        independents = fromList . (flip zip) (repeat S.empty) . snd . unzip $ ds
     in M.union dependents independents
 
-part1 :: Map Char (Set Char) -> String -> String
+part1 :: Deps -> String -> String
 part1 deps str
     | M.null deps = reverse str
     | otherwise =
         let available = fst . findMin . M.filter S.null $ deps
         in  part1 (fmap (S.delete available) (M.delete available deps)) (available:str)
 
+part2 :: Deps -> [Worker] -> Int -> Int
+part2 deps workers time
+    | M.null deps = time + (maximum . snd . unzip $ workers)
+    | otherwise =
+        let elapsedTime            = minOrDefault 0 . filter (/= 0) . snd . unzip $ workers
+            (done, working)        = partition ((== 0) . snd) . map (second $ max 0 . subtract elapsedTime) $ workers
+            clearedDeps            = foldr (fmap . S.delete) deps . map fst $ done
+            (newWorkers, newDeps)  = foldr assign (working, clearedDeps) $ [1 .. length done]
+        in  part2 newDeps newWorkers (time + elapsedTime)
+        where
+            minOrDefault n ns = if null ns then n else minimum ns
+            len task = fromEnum task - fromEnum 'A' + 61
+            assign :: Int -> ([Worker], Deps) -> ([Worker], Deps)
+            assign _ (w, d)
+                | M.null $ M.filter S.null d = ((emptyWorker:w), d)
+                | otherwise =
+                    let task = fst . findMax . M.filter S.null $ d
+                    in  (((task, len task):w), (M.delete task d))
+
 main :: IO ()
 main = do
-    input <- map parse . lines <$> readFile "input/07.txt"
-    putStrLn $ part1 (dependencies input) ""
+    input <- dependencies . map parse . lines <$> readFile "input/07.txt"
+    putStrLn $ part1 input ""
+    print    $ part2 input (replicate 5 emptyWorker) 0