Finally done day 24

[advent-of-code-19.git] / advent24 / src / advent24b.hs

diff --git a/advent24/src/advent24b.hs b/advent24/src/advent24b.hs
new file mode 100644 (file)
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+++ b/advent24/src/advent24b.hs
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+import Debug.Trace
+
+import qualified Data.Set as S
+
+data Cell = Cell { level :: Int
+                 , row :: Int
+                 , column :: Int
+                 } deriving (Show, Eq, Ord)
+type Grid = S.Set Cell
+
+
+gridSize = 5
+
+main :: IO ()
+main = 
+    do grid0 <- readGrid
+       print grid0
+       let finalGrid = head $ drop 200 $ iterate update grid0
+       print $ S.size finalGrid
+
+
+readGrid = 
+    do  gs <- readFile "data/advent24.txt"
+        let grid = lines gs
+        let isBug r c = (grid!!(r - 1))!!(c - 1) == '#'
+        let level = 0
+        return $ S.fromList [Cell {..} | row <- [1..gridSize], column <- [1..gridSize], isBug row column]
+
+neighbourSpaces :: Cell -> Grid
+neighbourSpaces cell = 
+     (  (neighbourSpacesLeft cell)
+     <> (neighbourSpacesRight cell)
+     <> (neighbourSpacesAbove cell)
+     <> (neighbourSpacesBelow cell)
+     )
+
+neighbourSpacesLeft :: Cell -> Grid
+neighbourSpacesLeft (Cell {..}) 
+  | column == 4 && row == 3 = S.fromList  [ Cell { level = (level + 1), row = r, column = 5} | r <- [1..gridSize] ]
+  | column == 1             = S.singleton ( Cell { level = (level - 1), row = 3, column = 2})
+  | otherwise               = S.singleton ( Cell { level, row, column = (column - 1)})
+
+neighbourSpacesRight :: Cell -> Grid
+neighbourSpacesRight (Cell {..}) 
+  | column == 2 && row == 3 = S.fromList  [ Cell { level = (level + 1), row = r, column = 1} | r <- [1..gridSize] ]
+  | column == 5             = S.singleton ( Cell { level = (level - 1), row = 3, column = 4})
+  | otherwise               = S.singleton ( Cell { level, row, column = (column + 1)})
+
+neighbourSpacesAbove :: Cell -> Grid
+neighbourSpacesAbove (Cell {..}) 
+  | row == 4 && column == 3 = S.fromList  [ Cell { level = (level + 1), row = 5, column = c} | c <- [1..gridSize] ]
+  | row == 1                = S.singleton ( Cell { level = (level - 1), row = 2, column = 3})
+  | otherwise               = S.singleton ( Cell { level, row = (row - 1), column})
+
+neighbourSpacesBelow :: Cell -> Grid
+neighbourSpacesBelow (Cell {..}) 
+  | row == 2 && column == 3 = S.fromList  [ Cell { level = (level + 1), row = 1, column = c} | c <- [1..gridSize] ]
+  | row == 5                = S.singleton ( Cell { level = (level - 1), row = 4, column = 3})
+  | otherwise               = S.singleton ( Cell { level, row = (row + 1), column})
+
+
+countOccupiedNeighbours :: Cell -> Grid -> Int
+countOccupiedNeighbours cell grid = S.size $ S.intersection grid $ neighbourSpaces cell
+
+bugSurvives :: Grid -> Cell -> Bool
+bugSurvives grid cell = alive && oneNeighbour
+  where alive = cell `S.member` grid
+        oneNeighbour = (countOccupiedNeighbours cell grid) == 1
+
+bugBorn :: Grid -> Cell -> Bool
+bugBorn grid cell = dead && (nNbrs == 1 || nNbrs == 2)
+  where dead = cell `S.notMember` grid
+        nNbrs = countOccupiedNeighbours cell grid
+
+update :: Grid -> Grid
+update grid = S.union (S.filter (bugSurvives grid) bugs) (S.filter (bugBorn grid) empties)
+  where bugs = grid
+        empties = (S.foldr mergeEmpties S.empty grid) `S.difference` bugs
+        mergeEmpties cell acc = S.union acc $ neighbourSpaces cell
+