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Improve Day 18, Puzzle 1 solution

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This commit is contained in:
daniele 2024-12-19 08:45:24 +01:00
parent aa89f22040
commit 0176c6b5df
Signed by: fuxino
GPG Key ID: 981A2B2A3BBF5514
1 changed files with 6 additions and 7 deletions

13
src/Day18/Puzzle1.hs

@ -4,7 +4,7 @@ import Data.Array (Array, indices, listArray, (!), (//))
import Data.Function (on)
import Data.List (minimumBy)
import Data.List.Split (splitOn)
import qualified Data.Map as M
import qualified Data.Map.Strict as M
import qualified Data.Set as S
type Coords = (Int, Int)
@ -48,11 +48,10 @@ initDijkstraState start g =
}
in s {distances = M.adjust (const (Dist 0)) start (distances s)}
updateDistances :: Graph -> M.Map Coords (Distance Int) -> Coords -> M.Map Coords (Distance Int)
updateDistances graph dists coords =
let nodes = edges graph M.! coords
dist = dists M.! coords
in M.mapWithKey (\k d -> if k `elem` nodes && d > dist then addDistance dist (Dist 1) else d) dists
updateDistances :: Graph -> M.Map Coords (Distance Int) -> [Coords] -> Distance Int -> M.Map Coords (Distance Int)
updateDistances _ dists [] _ = dists
updateDistances graph dists (n:nodes) startD =
updateDistances graph (M.adjust (const (addDistance startD (Dist 1))) n dists) nodes startD
findShortestPath :: Graph -> DijkstraState -> Coords -> Coords -> Distance Int
findShortestPath graph state start end
@ -63,7 +62,7 @@ findShortestPath graph state start end
let newState =
state
{ unvisited = S.delete start (unvisited state),
distances = updateDistances graph (distances state) start
distances = updateDistances graph (distances state) (edges graph M.! start) (distances state M.! start)
}
nodes = S.toList $ unvisited newState
next = fst $ minimumBy (compare `on` snd) [(n, distances newState M.! n) | n <- nodes]