--- /dev/null
+-- Using the idea of canonical representation of buildings from
+-- https://andars.github.io/aoc_day11.html by Andrew Foote,
+-- plus my extension of represening the pairs as an integer.
+
+-- This version is A* search, using a list for the agenda.
+
+module Main(main) where
+
+import Data.List (subsequences, (\\), sort, sortOn, nub, findIndices)
+import Data.Ord (comparing)
+import Data.Char (isDigit)
+
+data Item = Generator String | Microchip String deriving (Show, Eq)
+type Floor = [Item]
+data Building = Building Int [Floor] deriving (Show, Eq)
+data CBuilding = CBuilding Int Integer deriving (Show, Eq)
+data Agendum = Agendum {current :: Building, trail :: [CBuilding], cost :: Int}
+
+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"]),
+ [],
+ []
+ ]
+
+building0 = Building 0 [
+ (sort [Generator "polonium", Generator "thulium",
+ Microchip "thulium", Generator "promethium"]),
+ (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"],
+ []]
+
+canonical :: Building -> CBuilding
+canonical (Building f floors) = CBuilding f (read $ filter (isDigit) $ show $ sort pairs)
+ where names = nub $ map (\(Generator n) -> n) $ filter (isGenerator) $ concat floors
+ floorOf (Generator g) = head (findIndices
+ (\fl -> (Generator g) `elem` fl)
+ floors)
+ floorOf (Microchip g) = head (findIndices
+ (\fl -> (Microchip g) `elem` fl)
+ floors)
+ pairs = foldl (\ps n -> (floorOf (Generator n), floorOf (Microchip n)):ps) [] names
+
+
+
+main :: IO ()
+main = do
+ part1
+ part2
+
+
+part1 :: IO ()
+part1 = print $ length $ trail $ aStar (initAgenda building1) []
+
+part2 :: IO ()
+part2 = print $ length $ trail $aStar (initAgenda building2) []
+
+initAgenda :: Building -> [Agendum]
+initAgenda b = [Agendum {current = b, trail=[], cost = estimateCost b}]
+
+
+aStar :: [Agendum] -> [CBuilding] -> Agendum
+aStar [] _ = Agendum {current=buildingTest, trail=[], cost=0}
+aStar (currentAgendum:agenda) closed =
+ if isGoal reached then currentAgendum
+ else if creached `elem` closed
+ then aStar agenda closed
+ else aStar newAgenda (creached:closed)
+ where
+ reached = current currentAgendum
+ creached = canonical reached
+ newAgenda =
+ sortOn (cost) $
+ agenda ++ (candidates currentAgendum closed)
+
+
+candidates :: Agendum -> [CBuilding] -> [Agendum]
+candidates agendum closed = newCandidates
+ where
+ candidate = current agendum
+ previous = trail agendum
+ succs = legalSuccessors $ successors candidate
+ excludable = previous ++ closed
+ nonloops = filter (\s -> not $ (canonical s) `elem` excludable) succs
+ newCandidates = map (\n -> makeAgendum n) nonloops
+ makeAgendum new = Agendum {current = new,
+ trail = (canonical candidate):previous,
+ cost = estimateCost new + length previous + 1}
+
+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 oldF oldFloors newF items = Building newF newFloors
+ where newFloors = map (updateFloor) $ zip [0..] oldFloors
+ 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
+
projects / advent-of-code-16.git / blobdiff