advent11h.hs

   1 import Data.List (subsequences, (\\), sort, sortOn, nub, findIndices)
   2 import Data.Ord (comparing)
   3 import Data.Char (isDigit)
   4
   5 data Item = Generator String | Microchip String deriving (Show, Eq)
   6 type Floor = [Item]
   7 data Building = Building Int [Floor] deriving (Show, Eq)
   8 -- data CBuilding = CBuilding Int [(Int, Int)] deriving (Show, Eq)
   9 data CBuilding = CBuilding Int Integer deriving (Show, Eq)
  10 data Agendum = Agendum {current :: Building, trail :: [CBuilding], cost :: Int}
  11
  12 instance Ord Item where
  13     compare (Generator a) (Generator b) = compare a b
  14     compare (Microchip a) (Microchip b) = compare a b
  15     compare (Generator _) (Microchip _) = LT
  16     compare (Microchip _) (Generator _) = GT
  17
  18 instance Ord Building where
  19     compare b1 b2 = comparing estimateCost b1 b2
  20
  21 building1 = Building 0 [
  22     (sort [Generator "polonium", Generator "thulium",
  23      Microchip "thulium", Generator "promethium", Generator "ruthenium",
  24      Microchip "ruthenium", Generator "cobalt", Microchip "cobalt"]),
  25     (sort [Microchip "polonium", Microchip "promethium"]),
  26     [],
  27     []
  28     ]
  29
  30 building0 = Building 0 [
  31     (sort [Generator "polonium", Generator "thulium",
  32      Microchip "thulium", Generator "promethium"]),
  33     (sort [Microchip "polonium", Microchip "promethium"]),
  34     [],
  35     []
  36     ]
  37
  38 building2 = Building 0 [
  39     (sort [Generator "polonium", Generator "thulium",
  40      Microchip "thulium", Generator "promethium", Generator "ruthenium",
  41      Microchip "ruthenium", Generator "cobalt", Microchip "cobalt",
  42      Generator "elerium", Microchip "elerium",
  43      Generator "dilithium", Microchip "dilithium"]),
  44     (sort [Microchip "polonium", Microchip "promethium"]),
  45     [],
  46     []
  47     ]
  48
  49
  50 buildingTest = Building 0 [
  51     sort([Microchip "hydrogen", Microchip "lithium"]),
  52     [Generator "hydrogen"],
  53     [Generator "lithium"],
  54     []]
  55
  56 canonical :: Building -> CBuilding
  57 -- canonical (Building f floors) = CBuilding f (sort pairs)
  58 canonical (Building f floors) = CBuilding f (read $ filter (isDigit) $ show $ sort pairs)
  59     where names = nub $ map (\(Generator n) -> n) $ filter (isGenerator) $ concat floors
  60           floorOf (Generator g) = head (findIndices
  61                                                 (\fl -> (Generator g) `elem` fl)
  62                                                 floors)
  63           floorOf (Microchip g) = head (findIndices
  64                                                 (\fl -> (Microchip g) `elem` fl)
  65                                                 floors)
  66           pairs = foldl (\ps n -> (floorOf (Generator n), floorOf (Microchip n)):ps) [] names
  67
  68
  69
  70 main :: IO ()
  71 main = do
  72     part1
  73     part2
  74
  75
  76 part1 :: IO ()
  77 part1 = print $ length $ trail $ hillClimb (initAgenda building1) []
  78 -- part1 = print $ length $ trail $
  79 --             aStar [Agendum {current = building1, trail=[], cost = estimateCost building1}] []
  80
  81 -- part2 :: IO ()
  82 -- part2 = print $ length $ init $ extractJust $ aStar [[building2]] []
  83
  84 part2 :: IO ()
  85 part2 = print $ length $ trail $ hillClimb (initAgenda building2) []
  86
  87 initAgenda :: Building -> [Agendum]
  88 initAgenda b = [Agendum {current = b, trail=[], cost = estimateCost b}]
  89
  90 hillClimb :: [Agendum] -> [CBuilding] -> Agendum
  91 hillClimb [] _ = Agendum {current=buildingTest, trail=[], cost=0}
  92 hillClimb (currentAgendum:agenda) closed =
  93     if isGoal reached then currentAgendum
  94     else if creached `elem` closed
  95         then hillClimb agenda closed
  96         else hillClimb newAgenda (creached:closed)
  97     where
  98         reached = current currentAgendum
  99         creached = canonical reached
 100         newAgenda =
 101             -- sortBy (\t1 t2 -> (cost t1) `compare` (cost t2)) $
 102             sortOn (cost) $
 103             agenda ++ (candidates currentAgendum closed)
 104
 105
 106 candidates :: Agendum -> [CBuilding] -> [Agendum]
 107 candidates agendum closed = newCandidates
 108     where
 109         candidate = current agendum
 110         previous = trail agendum
 111         succs = legalSuccessors $ successors candidate
 112         -- nonloops = (succs \\ previous) \\ closed
 113         excludable = previous ++ closed
 114         nonloops = filter (\s -> not $ (canonical s) `elem` excludable) succs
 115         newCandidates = map (\n -> makeAgendum n) nonloops
 116         makeAgendum new = Agendum {current = new,
 117                                     trail = (canonical candidate):previous,
 118                                     cost = estimateCost new}
 119
 120 isGoal :: Building -> Bool
 121 isGoal (Building f floors) =
 122     f+1 == height && (all (null) $ take f floors)
 123     where height = length floors
 124
 125 isLegal :: Building -> Bool
 126 isLegal (Building f floors) =
 127     null floor
 128     ||
 129     not (any (isGenerator) floor)
 130     ||
 131     any (safePair) pairs
 132     where floor = floors!!f
 133           pairs = [(i, j) | i <- floor, j <- floor, isGenerator i]
 134           safePair (Generator e, Microchip f) = e == f
 135           safePair (Generator _, Generator _) = False
 136
 137 isGenerator :: Item -> Bool
 138 isGenerator (Generator _) = True
 139 isGenerator (Microchip _) = False
 140
 141 successors :: Building -> [Building]
 142 successors (Building f floors) = [updateBuilding f floors nf is | nf <- nextFloors, is <- items]
 143     where
 144         floor = floors!!f
 145         items = filter (\is -> length is == 1 || length is == 2) $ subsequences floor
 146         nextFloors = if f == 0 then [1]
 147                      else if f+1 == length floors then [f-1]
 148                      else [f+1, f-1]
 149
 150 legalSuccessors :: [Building] -> [Building]
 151 legalSuccessors = filter (isLegal)
 152
 153 updateBuilding :: Int -> [Floor] -> Int -> [Item] -> Building
 154 updateBuilding oldF oldFloors newF items = Building newF newFloors
 155     where newFloors = map (updateFloor) $ zip [0..] oldFloors
 156           updateFloor (f, fl)
 157             | f == oldF = sort $ fl \\ items
 158             | f == newF = sort $ items ++ fl
 159             | otherwise = fl
 160
 161 estimateCost :: Building -> Int
 162 estimateCost (Building _ floors) =
 163     sum $ map (\(c, f) -> c * length f) $ zip [0..] $ reverse floors
 164