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I hate this...

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This commit is contained in:
pingu 2024-12-07 00:50:57 +01:00
parent 73797cd075
commit b06f15139a
1 changed files with 7 additions and 24 deletions
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31
app/6.hs
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@ -4,7 +4,6 @@ module Main where
import Data.Functor
import Data.List
import Data.Matrix hiding (trace)
import Debug.Trace
data Dir where
N,E,W,S :: Dir
@ -57,6 +56,12 @@ guardPos s = let
in
(y+1,x+1,d)
getMarked :: Matrix Pos -> [(Int,Int)]
getMarked s = zip [1..] (toLists s) >>= \(y,l) -> zip [1..] l >>= \case
(x,Marked) -> [(y,x)]
(x,Guard _) -> [(y,x)]
_ -> []
move :: Matrix Pos -> (Int, Int, Dir) -> Matrix Pos
move s (y,x,d) = let (y',x',d') = case d of
N -> (y-1,x,E)
@ -70,7 +75,6 @@ move s (y,x,d) = let (y',x',d') = case d of
Obstacle -> setElem (Guard d') (y,x) s
_ -> setElem (Guard d) (y',x') $ setElem Marked (y,x) s
traversal :: Matrix Pos -> Matrix Pos
traversal s = let i@(y,x,d) = guardPos s in
if | y == 1 && d == N -> s
@ -96,29 +100,8 @@ isLoop s v = let i@(y,x,d) = guardPos s
| elem i v -> True
| otherwise -> isLoop s' (i:v)
traversal' :: Matrix Pos -> [(Int,Int)] -> [(Int,Int)]
traversal' s v = let i@(y,x,d) = guardPos s
inf = case d of
N -> (y-1,x)
E -> (y,x+1)
W -> (y,x-1)
S -> (y+1,x)
in
if | y == 1 && d == N -> v
| y == nrows s && d == S -> v
| x == 1 && d == W -> v
| x == ncols s && d == E -> v
| otherwise ->
let t = (setElem Obstacle inf s) in
--trace ("t: " ++ show t) $
if isLoop t []
then traversal' (move s i) ((y,x):v)
else traversal' (move s i) v
solve2 :: Matrix Pos -> Int
solve2 s = length . (`traversal'` []) $ s
solve2 s = length . filter (`isLoop` []) . (<&> flip (setElem Obstacle) s) . (\\ [(\(a,b,_) -> (a,b)) $ guardPos s]) . getMarked . traversal $ s
main :: IO ()
main = readFile "inputs/6" <&> parse >>= \i ->