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Day 9 - Part 1 refactor with state

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This commit is contained in:
Jens Kadenbach
2022-12-09 17:56:20 +01:00
parent 9bd3d62eec
commit dc5a757eb6
2 changed files with 21 additions and 11 deletions
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28
src/Day9.hs
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@@ -19,7 +19,8 @@ module Day9
where where
import Control.Arrow ((>>>)) import Control.Arrow ((>>>))
import Data.List (nub) import Control.Monad.Trans.State.Strict (State, runState, modify)
import qualified Data.Set as S
newtype Move = Move (Int, Int) newtype Move = Move (Int, Int)
deriving (Show, Eq) deriving (Show, Eq)
@@ -49,17 +50,26 @@ type Pos = (Int, Int)
data Grid = Grid {h :: Pos, t :: Pos} deriving (Show, Eq) data Grid = Grid {h :: Pos, t :: Pos} deriving (Show, Eq)
recordPositions :: [Step] -> [Pos] data MovementLog = MovementLog { visited :: S.Set Pos, recordedSteps :: [Step] }
recordPositions steps = nub (lastTailPos:positions) deriving (Show, Eq)
appendOne :: (Pos, Step) -> MovementLog -> MovementLog
appendOne (p, s) (MovementLog v steps) =
MovementLog (S.insert p v) (s:steps)
recordPositions :: [Step] -> ([Pos], [Step])
recordPositions steps = (allPositions, allSteps)
where where
(positions, _, Grid { t = lastTailPos}) = recordPositions' [] steps startGrid allPositions = S.toList $ S.insert lastTailPos (visited state)
recordPositions' :: [Pos] -> [Step] -> Grid -> ([Pos], [Step], Grid) allSteps = reverse (recordedSteps state)
recordPositions' pos [] grid = (pos, [], grid) ((_, Grid { t = lastTailPos}), state) = runState (recordPositions' steps startGrid) (MovementLog S.empty [])
recordPositions' pos (m : ms) Grid {h = headPos, t = tailPos} = recordPositions' :: [Step] -> Grid -> State MovementLog ([Step], Grid)
recordPositions' [] grid = return ([], grid)
recordPositions' (m : ms) Grid {h = headPos, t = tailPos} =
let newHead = headPos `step` m let newHead = headPos `step` m
followStep = follow newHead tailPos followStep = follow newHead tailPos
newTail = tailPos `step` followStep newTail = tailPos `step` followStep
in recordPositions' (tailPos : pos) ms Grid {h = newHead, t = newTail} in modify (appendOne (newTail, followStep)) >> recordPositions' ms Grid {h = newHead, t = newTail}
startGrid :: Grid startGrid :: Grid
startGrid = Grid {h = p, t = p} startGrid = Grid {h = p, t = p}
@@ -106,5 +116,5 @@ day9 = do
input <- readFile "ressources/day09-input" input <- readFile "ressources/day09-input"
putStrLn "Day9" putStrLn "Day9"
let movements = parseMovements input let movements = parseMovements input
let positions = concatMap normalizeMovement >>> recordPositions >>> length $ movements let positions = concatMap normalizeMovement >>> recordPositions >>> fst >>> length $ movements
putStrLn ("Number of distinct positions " ++ show positions) putStrLn ("Number of distinct positions " ++ show positions)

4
test/Day9Spec.hs
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@@ -67,13 +67,13 @@ spec =
let positions = parseMovements let positions = parseMovements
>>> concatMap normalizeMovement >>> concatMap normalizeMovement
>>> recordPositions >>> recordPositions
>>> fst
>>> sort >>> sort
$ testInput $ testInput
length positions `shouldBe` 13 length positions `shouldBe` 13
positions `shouldBe` expectedPositions positions `shouldBe` expectedPositions
it "solves the riddle" $ do it "solves the riddle" $ do
input <- readFile "ressources/day09-input" input <- readFile "ressources/day09-input"
putStrLn "Day9"
let movements = parseMovements input let movements = parseMovements input
let positions = concatMap normalizeMovement >>> recordPositions >>> length $ movements let positions = concatMap normalizeMovement >>> recordPositions >>> fst >>> length $ movements
positions `shouldBe` 5878 positions `shouldBe` 5878