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Day 17 - fixed infinite loop (canFlood incorrect side boundaries), finished parts 1 and 2.

This commit is contained in:
Jonathan Chan 2018-12-18 11:18:47 -08:00
parent 50867bfd20
commit 3251270ee9
2 changed files with 45 additions and 25 deletions
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2
README.md
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@ -27,7 +27,7 @@ Now located in this repository's wiki.
| 13 | ~ 0.5 | | 13 | ~ 0.5 |
| 14 | 22.3 | | 14 | 22.3 |
| 15 | < 1 | | 15 | < 1 |
| 16 | | | 16 | ~ 15 |
| 17 | | | 17 | |
| 18 | | | 18 | |
| 19 | | | 19 | |

68
src/Day17.hs
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@ -1,11 +1,11 @@
{-# LANGUAGE TupleSections, BangPatterns #-} {-# LANGUAGE TupleSections #-}
module Day17 (main) where module Day17 (main) where
import Prelude hiding (lookup, filter) import Prelude hiding (lookup)
import Data.Foldable (maximumBy, minimumBy) import Data.Foldable (maximumBy, minimumBy)
import Data.Ord (comparing) import Data.Ord (comparing)
import Data.Map (Map, fromList, insert, lookup, filter, filterWithKey, keys, size) import Data.Map (Map, fromList, insert, lookup, filterWithKey, keys, size)
import Debug.Trace (traceShow, traceShowId) import Debug.Trace (traceShow, traceShowId)
-- Horz (left, right) y | Vert x (top, bottom) -- Horz (left, right) y | Vert x (top, bottom)
@ -21,12 +21,16 @@ parse str =
range = (read $ (takeWhile (/= '.') rangeString), (read . reverse . takeWhile (/= '.') . reverse $ rangeString)) range = (read $ (takeWhile (/= '.') rangeString), (read . reverse . takeWhile (/= '.') . reverse $ rangeString))
in if fstAxis == 'x' then Vert val range else Horz range val in if fstAxis == 'x' then Vert val range else Horz range val
createGrid :: [Vein] -> (Int, Grid) -- returns minimum y, maximum y, and grid
createGrid :: [Vein] -> (Int, Int, Grid)
createGrid veins = createGrid veins =
let maxY = getMaxY $ maximumBy (comparing getMaxY) veins let minY = getMinY $ minimumBy (comparing getMinY) veins
maxY = getMaxY $ maximumBy (comparing getMaxY) veins
grid = foldr insertVein (fromList [((500, 0), '|')]) veins grid = foldr insertVein (fromList [((500, 0), '|')]) veins
in (maxY, grid) in (minY, maxY, grid)
where where
getMinY (Horz _ y) = y
getMinY (Vert _ (top, _)) = top
getMaxY (Horz _ y) = y getMaxY (Horz _ y) = y
getMaxY (Vert _ (_, bottom)) = bottom getMaxY (Vert _ (_, bottom)) = bottom
insertVein (Horz (left, right) y) grid = foldr (\coord g -> insert coord '#' g) grid $ map (,y) [left..right] insertVein (Horz (left, right) y) grid = foldr (\coord g -> insert coord '#' g) grid $ map (,y) [left..right]
@ -77,26 +81,42 @@ flood coord grid =
canFlood :: Coordinate -> Grid -> Bool canFlood :: Coordinate -> Grid -> Bool
canFlood (x, y) grid = canFlood (x, y) grid =
(Just '|' /= lookup (x - 1, y) grid || let validSides = (lookup (x - 1, y) grid, lookup (x + 1, y) grid) `notElem` [(Just '#', Just '|'), (Just '|', Just '#'), (Just '|', Just '|')]
Just '|' /= lookup (x + 1, y) grid) && validBottom = lookup (x, y + 1) grid `elem` [Just '#', Just '~']
case lookup (x, y + 1) grid of in validSides && validBottom
Just '#' -> True
Just '~' -> True
_ -> False
flowFlood :: Int -> Grid -> Grid {-
flowFlood maxY grid = A few edge cases:
let flowable = keys $ filterWithKey (\k v -> v == '|' && canFlowDown maxY k grid) grid * Flowing water with more flowing water on one side (. | | or | | .) could flow into the gap
flowed = foldr (flowDown maxY) grid flowable . | | | | |
floodable = keys $ filterWithKey (\k v -> v == '|' && canFlood k flowed) flowed . # | => | # |
flooded = foldr flood flowed floodable . # | | # |
in if null flowable && null floodable then grid else flowFlood maxY flooded * Flowing water surrounded by walls should become stagnant
# | # # ~ #
# | # => # ~ #
# # # # # #
* But flowing water between a wall and more flowing water never changes
and neither does flowing water between more flowing water
# | | |
# # # |
-}
part1 :: Int -> Grid -> Int floodFlow :: Int -> Grid -> Grid
part1 maxY grid = subtract 1 . size . filter (\v -> v == '|' || v == '~') . flowFlood maxY $ grid floodFlow maxY grid =
let floodable = keys $ filterWithKey (\k v -> v == '|' && canFlood k grid) grid
flooded = foldr flood grid floodable
flowable = keys $ filterWithKey (\k v -> v == '|' && canFlowDown maxY k flooded) flooded
flowed = foldr (flowDown maxY) flooded flowable
in if null flowable && null floodable then grid else floodFlow maxY flowed
part1 :: Int -> Int -> Grid -> Int
part1 minY maxY grid = size . filterWithKey (\(_, y) v -> y >= minY && y <= maxY && (v == '|' || v == '~')) . floodFlow maxY $ grid
part2 :: Int -> Int -> Grid -> Int
part2 minY maxY grid = size . filterWithKey (\(_, y) v -> y >= minY && y <= maxY && v == '~') . floodFlow maxY $ grid
main :: IO () main :: IO ()
main = do main = do
(maxY, grid) <- createGrid . map parse . lines <$> readFile "input/17.txt" (minY, maxY, grid) <- createGrid . map parse . lines <$> readFile "input/17.txt"
print $ maxY print $ part1 minY maxY grid
print $ part1 maxY grid print $ part2 minY maxY grid