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rewrite to not keep track of path

This commit is contained in:
Quinten Kock 2021-12-13 01:11:17 +01:00
parent 7c4c119eff
commit 8031b0327a
1 changed files with 13 additions and 13 deletions
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26
2021/day12.hs
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@ -4,8 +4,10 @@ import Data.Map ( Map, fromList, unionWith, empty, (!) )
import Data.List.Split (splitOn)
import qualified Data.Char
type Path = (String,String)
type System = Map String [String]
type Cave = String
type Path = (Cave,Cave)
type System = Map Cave [Cave]
readPath :: String -> Path
readPath s = (from,to) where [from,to] = splitOn "-" s
@ -13,19 +15,17 @@ readPath s = (from,to) where [from,to] = splitOn "-" s
addPath :: Path -> System -> System
addPath (from,to) = unionWith (++) (Data.Map.fromList [(from,[to]), (to,[from])])
isUpper :: String -> Bool
isUpper :: Cave -> Bool
isUpper = Data.Char.isUpper . head
pathFinder :: System -> [String] -> HashSet String -> Int
pathFinder _ [] _ = error "no starting point!"
pathFinder sys p@("end":xs) _ = 1
pathFinder sys p@(x:xs) visited = sum $ map (\next -> pathFinder sys (next:p) (next `insert` visited)) elig
pathFinder :: System -> Cave -> HashSet Cave -> Int
pathFinder sys "end" _ = 1
pathFinder sys x visited = sum $ map (\next -> pathFinder sys next (next `insert` visited)) elig
where elig = filter (\cave -> isUpper cave || not (cave `member` visited)) (sys ! x)
pathFinder2 :: System -> [String] -> HashSet String -> Int
pathFinder2 _ [] _ = error "no starting point!"
pathFinder2 sys p@("end":xs) _ = 1
pathFinder2 sys p@(x:xs) visited = sum $ map (\next -> f next sys (next:p) (next `insert` visited)) elig
pathFinder2 :: System -> Cave -> HashSet Cave -> Int
pathFinder2 sys "end" _ = 1
pathFinder2 sys x visited = sum $ map (\next -> f next sys next (next `insert` visited)) elig
where
f cave = if isUpper cave || not (cave `member` visited) then pathFinder2 else pathFinder
elig = filter (/= "start") (sys ! x)
@ -36,7 +36,7 @@ main = do
let system = foldr addPath Data.Map.empty input
putStrLn "part 1: "
print $ pathFinder system ["start"] (Data.HashSet.fromList ["start"])
print $ pathFinder system "start" (Data.HashSet.fromList ["start"])
putStrLn "part 2: "
print $ pathFinder2 system ["start"] (Data.HashSet.fromList ["start"])
print $ pathFinder2 system "start" (Data.HashSet.fromList ["start"])