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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 |
| 14 | 22.3 |
| 15 | < 1 |
| 16 | |
| 16 | ~ 15 |
| 17 | |
| 18 | |
| 19 | |

68
src/Day17.hs
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@ -1,11 +1,11 @@
{-# LANGUAGE TupleSections, BangPatterns #-}
{-# LANGUAGE TupleSections #-}
module Day17 (main) where
import Prelude hiding (lookup, filter)
import Prelude hiding (lookup)
import Data.Foldable (maximumBy, minimumBy)
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)
-- Horz (left, right) y | Vert x (top, bottom)
@ -21,12 +21,16 @@ parse str =
range = (read $ (takeWhile (/= '.') rangeString), (read . reverse . takeWhile (/= '.') . reverse $ rangeString))
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 =
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
in (maxY, grid)
in (minY, maxY, grid)
where
getMinY (Horz _ y) = y
getMinY (Vert _ (top, _)) = top
getMaxY (Horz _ y) = y
getMaxY (Vert _ (_, bottom)) = bottom
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 (x, y) grid =
(Just '|' /= lookup (x - 1, y) grid ||
Just '|' /= lookup (x + 1, y) grid) &&
case lookup (x, y + 1) grid of
Just '#' -> True
Just '~' -> True
_ -> False
let validSides = (lookup (x - 1, y) grid, lookup (x + 1, y) grid) `notElem` [(Just '#', Just '|'), (Just '|', Just '#'), (Just '|', Just '|')]
validBottom = lookup (x, y + 1) grid `elem` [Just '#', Just '~']
in validSides && validBottom
flowFlood :: Int -> Grid -> Grid
flowFlood maxY grid =
let flowable = keys $ filterWithKey (\k v -> v == '|' && canFlowDown maxY k grid) grid
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
{-
A few edge cases:
* Flowing water with more flowing water on one side (. | | or | | .) could flow into the gap
. | | | | |
. # | => | # |
. # | | # |
* 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
part1 maxY grid = subtract 1 . size . filter (\v -> v == '|' || v == '~') . flowFlood maxY $ grid
floodFlow :: Int -> Grid -> 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 = do
(maxY, grid) <- createGrid . map parse . lines <$> readFile "input/17.txt"
print $ maxY
print $ part1 maxY grid
(minY, maxY, grid) <- createGrid . map parse . lines <$> readFile "input/17.txt"
print $ part1 minY maxY grid
print $ part2 minY maxY grid