X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=advent09%2FMain.hs;h=df5b1be8e413054286c52e43ce7928209f59d0d7;hb=e2b15781f674220586e860fb9a85b6ad0f278fad;hp=4cd269e3f42cce4cbfad67d0b33ff320e4379587;hpb=150f4ed9cd6cf5a7a29de631eb9b6ff9802dc88d;p=advent-of-code-21.git

diff --git a/advent09/Main.hs b/advent09/Main.hs
index 4cd269e..df5b1be 100644
--- a/advent09/Main.hs
+++ b/advent09/Main.hs
@@ -1,30 +1,25 @@
--- Writeup at https://work.njae.me.uk/2021/12/09/advent-of-code-2021-day-8/
-
+-- Writeup at https://work.njae.me.uk/2021/12/09/advent-of-code-2021-day-9/
 
 import Data.Array 
 import Data.Char
--- import Data.Maybe
-import Data.List hiding ((\\))
+import Data.List (sort)
 import qualified Data.Set as S
 import Data.Set ((\\))
+import Linear (V2(..), (^+^))
 
-
-type Coord = (Int, Int) -- (row, column)
+type Coord = V2 Int
 type Grid = Array Coord Int
 type Basin = S.Set Coord
 
 main :: IO ()
 main = 
-  do  text <- readFile "data/advent09.txt"
+  do  text <- readFile "data/advent09a.txt"
       let grid = mkGrid text
-      print $ bounds grid
       print $ part1 grid
-      -- print $ lowPoints grid
-      -- print $ breadthFirstSearch grid (S.singleton (4, 6)) S.empty
       print $ part2 grid
 
 mkGrid :: String -> Grid
-mkGrid text = listArray ((0, 0), (r, c)) $ map digitToInt $ concat rows
+mkGrid text = listArray ((V2 0 0), (V2 r c)) $ map digitToInt $ concat rows
   where rows = lines text
         r = length rows - 1
         c = (length $ head rows) - 1
@@ -68,18 +63,8 @@ breadthFirstSearch grid agenda basin
                  else S.insert here basin
         agenda' = S.union candidates $ S.delete here agenda
 
-
 neighbours :: Grid -> Coord -> [Coord]
-neighbours grid (r, c) = filter (gValid grid)  
-  [ (r + dr, c + dc) 
-  | (dr, dc) <- [(-1, 0), (1, 0), (0, -1), (0, 1)]
+neighbours grid here = filter (inRange (bounds grid))  
+  [ here ^+^ delta 
+  | delta <- [V2 -1 0, V2 1 0, V2 0 -1, V2 0 1]
   ]
-
-gValid :: Grid -> Coord -> Bool
-gValid grid (r, c)
-  | r < minR = False
-  | c < minC = False
-  | r > maxR = False
-  | c > maxC = False
-  | otherwise = True
-  where ((minR, minC), (maxR, maxC)) = bounds grid