From: Neil Smith <neil.git@njae.me.uk>
Date: Sun, 12 Dec 2021 10:33:15 +0000 (+0000)
Subject: Done day 11
X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;ds=sidebyside;h=5906e1d8d0723d8c7e3d97c3a29988723efe2f71;p=advent-of-code-21.git

Done day 11
---

diff --git a/advent-of-code21.cabal b/advent-of-code21.cabal
index 626e0ae..12cd8ab 100644
--- a/advent-of-code21.cabal
+++ b/advent-of-code21.cabal
@@ -134,3 +134,8 @@ executable advent10
   import: common-extensions, build-directives
   main-is: advent10/Main.hs
   build-depends: containers
+
+executable advent11
+  import: common-extensions, build-directives
+  main-is: advent11/Main.hs
+  build-depends: array, containers, linear
diff --git a/advent11/Main.hs b/advent11/Main.hs
new file mode 100644
index 0000000..a74f4fa
--- /dev/null
+++ b/advent11/Main.hs
@@ -0,0 +1,89 @@
+-- Writeup at https://work.njae.me.uk/2021/12/09/advent-of-code-2021-day-9/
+
+import Data.Array.IArray
+import Data.Char
+import Linear (V2(..), (^+^))
+
+type Coord = V2 Int
+type Grid = Array Coord Octopus
+
+data Octopus = Octopus Int Bool
+  deriving (Ord, Eq, Show)
+
+main :: IO ()
+main = 
+  do  text <- readFile "data/advent11.txt"
+      let grid = mkGrid text
+      print $ part1 grid
+      print $ part2 grid
+
+mkGrid :: String -> Grid
+mkGrid text = listArray ((V2 0 0), (V2 r c)) $ map mkOct $ concat rows
+  where rows = lines text
+        r = length rows - 1
+        c = (length $ head rows) - 1
+        mkOct e = Octopus (digitToInt e) False
+
+part1 grid = snd $ (simulate grid) !! 100
+
+part2 grid = length $ takeWhile notSyncronised $ simulate grid
+  where notSyncronised (g, _) = not $ simultaneous g
+
+simulate :: Grid -> [(Grid, Int)]
+simulate grid = iterate step (grid, 0)
+
+step :: (Grid, Int) -> (Grid, Int)
+step (grid0, flashCount0) = (grid3, flashCount0 + numFlashers)
+  where grid1 = increment grid0
+        triggers = findFlashers grid1
+        grid2 = flash grid1 triggers
+        flashers = findFlashers grid2
+        numFlashers = length flashers
+        grid3 = resetFlashers grid2 flashers
+
+
+simultaneous grid = all zeroOct $ elems grid
+  where zeroOct (Octopus 0 _) = True
+        zeroOct _ = False
+
+increment :: Grid -> Grid
+increment = amap incrementOne
+
+incrementSome grid locations = grid // (zip locations incrementedOcts)
+  where incrementedOcts = map (incrementOne . (grid !)) locations
+
+incrementOne (Octopus energy flashed) = Octopus (energy + 1) flashed 
+
+
+findFlashers :: Grid -> [Coord]
+findFlashers = map fst . filter (overpowered . snd) . assocs
+  where overpowered (Octopus energy _) = energy > 9
+
+
+flash grid [] = grid
+flash grid (here:agenda) 
+  | flashed == True = flash grid agenda
+  | energy <= 9 = flash grid agenda
+  | otherwise = flash grid'' agenda'
+    -- set this as flashed
+    -- increment neighbours
+    -- add negighbours to agenda
+  where Octopus energy flashed = grid ! here
+        nbrs = neighbours grid here
+        octopus' = Octopus (energy + 1) True
+        agenda' = nbrs ++ agenda
+        grid' = grid // [(here, octopus')]
+        grid'' = incrementSome grid' nbrs
+
+resetFlashers :: Grid -> [Coord] -> Grid
+resetFlashers grid locations = grid // (zip locations resetOcts)
+  where resetOcts = repeat (Octopus 0 False)
+
+
+neighbours :: Grid -> Coord -> [Coord]
+neighbours grid here = filter (inRange (bounds grid))  
+  [ here ^+^ (V2 r c)
+  | r <- [-1, 0, 1]
+  , c <- [-1, 0, 1]
+  , (r, c) /= (0, 0)
+  ]
diff --git a/data/advent11.txt b/data/advent11.txt
new file mode 100644
index 0000000..89cabdc
--- /dev/null
+++ b/data/advent11.txt
@@ -0,0 +1,10 @@
+3265255276
+1537412665
+7335746422
+6426325658
+3854434364
+8717377486
+4522286326
+6337772845
+8824387665
+6351586484
\ No newline at end of file
diff --git a/data/advent11a.txt b/data/advent11a.txt
new file mode 100644
index 0000000..a3819c9
--- /dev/null
+++ b/data/advent11a.txt
@@ -0,0 +1,10 @@
+5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526
\ No newline at end of file