144 lines
4.6 KiB
Agda
144 lines
4.6 KiB
Agda
module Day21
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import Prelude
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import Node
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import Aoc
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import SortedMap
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import Parser
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min : Int → Int → Int
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min a b = if a < b then a else b
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gridPoints : String → List (Char × Int × Int)
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gridPoints text = go 0 0 (unpack text) Nil
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where
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-- might as well be tail recursive
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go : Int → Int → List Char → List (Char × Int × Int) → List (Char × Int × Int)
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go row col Nil points = points
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go row col ('\n' :: cs) points = go (row + 1) 0 cs points
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go row col (c :: cs) points = go row (col + 1) cs ((c,row,col) :: points)
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data Dir : U where North East South West : Dir
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dirs : List Dir
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dirs = (North :: South :: East :: West :: Nil)
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move : Point → Dir → Point
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move (r, c) North = (r - 1, c)
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move (r, c) East = (r, c + 1)
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move (r, c) South = (r + 1, c)
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move (r, c) West = (r, c - 1)
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Costs : U
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Costs = SortedMap (Point × Point) Int
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-- linked list of keypads
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record Keypad where
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constructor KP
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name : String
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start : Point
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interdit : Point
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costs : Costs -- cache of costs
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next : Maybe Keypad
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getPaths : Point → Point → Point → List (List Dir)
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getPaths interdit pt@(a,b) to@(c,d) =
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if pt == to then Nil :: Nil else
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if pt == interdit then Nil else
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join $ map check dirs
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where
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check : Dir → List (List Dir)
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check North = if c < a then map (_::_ North) $ getPaths interdit (move pt North) (c,d) else Nil
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check South = if a < c then map (_::_ South) $ getPaths interdit (move pt South) (c,d) else Nil
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check East = if b < d then map (_::_ East) $ getPaths interdit (move pt East) (c,d) else Nil
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check West = if d < b then map (_::_ West) $ getPaths interdit (move pt West) (c,d) else Nil
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updateCost : Point × Point → Int → Keypad → Keypad
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updateCost path cost (KP n s i c nxt) = (KP n s i (updateMap path cost c) nxt)
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keyPos : Dir → Point
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keyPos North = (0,1)
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keyPos South = (1,1)
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keyPos East = (1,2)
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keyPos West = (1,0)
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-- cost to run a path in a keypad
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pathCost : Point → Point → Keypad → Keypad × Int
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-- cost of sequence of points (run in parent keypad)
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-- for numpad, we pick points from the map, for the rest map keyPos ...
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seqCost : Point → List Point → Keypad × Int → Keypad × Int
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seqCost cur Nil (kp, cost) = (kp, cost)
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seqCost cur (pt :: pts) (kp, cost) =
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let (kp, cost') = pathCost cur pt kp in
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seqCost pt pts (kp, cost + cost')
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-- cost of best path from -> to in kp
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pathCost from to kp =
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case lookupMap (from, to) kp.costs of
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Just (_, cost) => (kp, cost)
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Nothing =>
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let (path :: paths) = getPaths kp.interdit from to | _ => ? in
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case kp of
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(KP n s i c Nothing) => (kp, 1)
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(KP n s i c (Just kp')) =>
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let (kp', cost) = mincost path paths kp' in
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let kp = KP n s i c (Just kp') in
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(updateCost (from,to) cost kp, cost)
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where
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xlate : List Dir → Point -> List Point
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xlate Nil a = a :: Nil
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xlate (d :: ds) a = keyPos d :: xlate ds a
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mincost : List Dir → List (List Dir) → Keypad → Keypad × Int
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mincost path paths kp =
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let (kp', cost) = seqCost (0,2) (xlate path kp.start) (kp, 0) in
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case paths of
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Nil => (kp', cost)
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(path :: paths) => let (kp', cost') = mincost path paths kp' in (kp', min cost cost')
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fromList : ∀ k v. {{Ord k}} {{Eq k}} → List (k × v) → SortedMap k v
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fromList xs = foldMap (\ a b => b) EmptyMap xs
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getNum : String → Int
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getNum str = case number (unpack str) of
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Right (n, _) => n
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_ => 0
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runOne : Keypad → SortedMap Char Point → String → Int × Int
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runOne kp numpad str =
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let pts = map snd $ mapMaybe (flip lookupMap numpad) $ unpack str in
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let res = seqCost (3,2) pts (kp, 0) in
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(getNum str, snd res)
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makeKeypad : Int → Keypad -> Keypad
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makeKeypad 0 kp = kp
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makeKeypad n kp = makeKeypad (n - 1) $ KP (show n) (0,2) (0,0) EmptyMap (Just kp)
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run : String -> IO Unit
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run fn = do
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putStrLn fn
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text <- readFile fn
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let codes = split (trim text) "\n"
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-- the space is illegal spot
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let numpad = fromList $ filter (not ∘ _==_ ' ' ∘ fst) $ gridPoints "789\n456\n123\n 0A"
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debugLog $ toList numpad
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let rob1 = KP "r1" (0,2) (0,0) EmptyMap Nothing
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let robn = makeKeypad 2 rob1
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let kp = KP "kp" (3,2) (3,0) EmptyMap (Just robn)
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let p1 = foldl _+_ 0 $ map (uncurry _*_ ∘ runOne kp numpad) codes
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putStrLn $ "part1 " ++ show p1
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let rob1 = KP "r1" (0,2) (0,0) EmptyMap Nothing
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let robn = makeKeypad 25 rob1
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let kp = KP "kp" (3,2) (3,0) EmptyMap (Just robn)
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let p2 = foldl _+_ 0 $ map (uncurry _*_ ∘ runOne kp numpad) codes
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putStrLn $ "part2 " ++ show p2
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main : IO Unit
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main = do
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run "aoc2024/day21/eg.txt"
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run "aoc2024/day21/input.txt"
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