Day 11

diff --git a/advent11.hs b/advent11.hs
new file mode 100644 (file)
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--- /dev/null
+++ b/advent11.hs
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+import Data.List (subsequences, (\\), sort, sortBy)
+import Data.Ord (comparing)
+
+data Item = Generator String | Microchip String deriving (Show, Eq)
+type Floor = [Item]
+data Building = Building Int [Floor] deriving (Show, Eq)
+
+instance Ord Item where
+    compare (Generator a) (Generator b) = compare a b
+    compare (Microchip a) (Microchip b) = compare a b
+    compare (Generator _) (Microchip _) = LT
+    compare (Microchip _) (Generator _) = GT
+
+instance Ord Building where
+    compare b1 b2 = comparing estimateCost b1 b2
+
+building1 = Building 0 [
+    (sort [Generator "polonium", Generator "thulium", 
+     Microchip "thulium", Generator "promethium", Generator "ruthenium",
+     Microchip "ruthenium", Generator "cobalt", Microchip "cobalt"]),
+    (sort [Microchip "polonium", Microchip "promethium"]),
+    [],
+    []
+    ]
+
+building2 = Building 0 [
+    (sort [Generator "polonium", Generator "thulium", 
+     Microchip "thulium", Generator "promethium", Generator "ruthenium",
+     Microchip "ruthenium", Generator "cobalt", Microchip "cobalt",
+     Generator "elerium", Microchip "elerium",
+     Generator "dilithium", Microchip "dilithium"]),
+    (sort [Microchip "polonium", Microchip "promethium"]),
+    [],
+    []
+    ]
+
+
+buildingTest = Building 0 [
+    sort([Microchip "hydrogen", Microchip "lithium"]),
+    [Generator "hydrogen"],
+    [Generator "lithium"],
+    []]
+
+main :: IO ()
+main = do 
+    part1 
+    part2 
+
+
+part1 :: IO ()
+-- part1 = print $ length $ init $ extractJust $ aStar [[buildingTest]] []
+part1 = print $ length $ init $ extractJust $ aStar [[building1]] []
+
+part2 :: IO ()
+part2 = print $ length $ init $ extractJust $ aStar [[building2]] []
+
+
+extractJust :: Maybe [a] -> [a]
+extractJust Nothing = []
+extractJust (Just x) = x
+
+aStar :: [[Building]] -> [Building] -> Maybe [Building]
+aStar [] _ = Nothing
+aStar (currentTrail:trails) closed = 
+    if isGoal (head currentTrail) then Just currentTrail
+    else aStar newAgenda ((head currentTrail): closed) 
+    where newAgenda = 
+            sortBy (\t1 t2 -> (head t1) `compare` (head t2)) $ 
+            trails ++ (candidates currentTrail closed)
+
+candidates :: [Building] -> [Building] -> [[Building]]
+candidates currentTrail closed = newCandidates
+    where
+        (candidate:trail) = currentTrail
+        succs = legalSuccessors $ successors candidate
+        nonloops = (succs \\ trail) \\ closed
+        newCandidates = map (\n -> n:candidate:trail) nonloops
+
+isGoal :: Building -> Bool
+isGoal (Building f floors) =
+    f+1 == height && (all (null) $ take f floors)
+    where height = length floors
+
+isLegal :: Building -> Bool
+isLegal (Building f floors) = 
+    null floor 
+    ||
+    not (any (isGenerator) floor)
+    ||
+    any (safePair) pairs
+    where floor = floors!!f
+          pairs = [(i, j) | i <- floor, j <- floor, isGenerator i]
+          safePair (Generator e, Microchip f) = e == f
+          safePair (Generator _, Generator _) = False
+
+isGenerator :: Item -> Bool
+isGenerator (Generator _) = True
+isGenerator (Microchip _) = False
+
+successors :: Building -> [Building]
+successors (Building f floors) = [updateBuilding f floors nf is | nf <- nextFloors, is <- items]
+    where 
+        floor = floors!!f
+        items = filter (\is -> length is == 1 || length is == 2) $ subsequences floor
+        nextFloors = if f == 0 then [1]
+                     else if f+1 == length floors then [f-1]
+                     else [f+1, f-1]
+
+legalSuccessors :: [Building] -> [Building]
+legalSuccessors = filter (isLegal)
+
+updateBuilding :: Int -> [Floor] -> Int -> [Item] -> Building
+-- updateBuilding f floors _ _ = Building f floors
+updateBuilding oldF oldFloors newF items = Building newF newFloors
+    where numberedFloors = zip [0..] oldFloors
+          newFloors = map (updateFloor) numberedFloors
+          updateFloor (f, fl) 
+            | f == oldF = sort $ fl \\ items
+            | f == newF = sort $ items ++ fl
+            | otherwise = fl
+
+estimateCost :: Building -> Int
+estimateCost (Building _ floors) = 
+    sum $ map (\(c, f) -> c * length f) $ zip [0..] $ reverse floors
+