[Day 02] Part 2: brute force, naïve, slow. I'm sure it would get there eventually...

1 files changed, 30 insertions, 4 deletions

diff --git a/day06/day06.hs b/day06/day06.hs
index fa022f7..3f11fed 100644
--- a/day06/day06.hs
+++ b/day06/day06.hs
@@ -67,16 +67,42 @@ el ?: arr
 
 route :: Grid -> [Coo] -> Guard -> [Coo]
 route grid seen guard@(coo, dir)
-  | nguard == Nothing     = coo ?: seen
-  | otherwise = route grid (coo ?: seen) (fromJust nguard)
+  | nguard == Nothing = coo ?: seen
+  | otherwise         = route grid (coo ?: seen) (fromJust nguard)
   where
     nguard = step grid guard
 
+route2 :: Grid -> [Guard] -> Bool
+route2 grid seen@(guard:_)
+  | nguard == Nothing             = False
+  | (fromJust nguard) `elem` seen = True
+  | otherwise                     = route2 grid ((fromJust nguard):seen)
+  where
+    nguard = step grid guard
+
+putObs :: Grid -> Coo -> Grid
+putObs grid (r, c) =
+  let (br,tr:ar) = splitAt r grid
+      (bc,_:ac)  = splitAt c tr in
+        br ++
+        [bc ++ [Obs] ++ ac] ++
+        ar
+
 part1 :: Grid -> Guard -> Int
-part1 grid guard = length $ route grid [] guard
+part1 grid guard =
+  length $ route grid [] guard
+
+part2 :: Grid -> Guard -> Int
+part2 grid guard =
+  length $
+    filter (route2A . putObsA) $
+    route grid [] guard
+  where
+    route2A = (flip route2) [guard]
+    putObsA = putObs grid
 
 main = do
   file <- readFile "day06.input"
   let (grid, guard) = consume file
   putStrLn ("Part 1: " ++ (show $ part1 grid guard))
-  --putStrLn ("Part 2: " ++ (show $ part2 lns))
+  putStrLn ("Part 2: " ++ (show $ part2 grid guard))