Complete day 3

1 files changed, 15 insertions, 0 deletions

diff --git a/2019/3.hs b/2019/3.hs
index 7f0180a..b0f8e71 100644
--- a/2019/3.hs
+++ b/2019/3.hs
@@ -2,6 +2,7 @@ module Main where
 
 import Data.Char
 import Data.List
+import qualified Data.Map.Strict as Map
 import qualified Data.Set as Set
 
 import Input
@@ -48,8 +49,22 @@ points (Seg pt dir n) =
 manhattan :: Pt -> Int
 manhattan (Pt x y) = abs x + abs y
 
+data Hit = Hit {hitPt :: Pt, hitIdx :: Int} deriving (Show)
+instance Eq Hit where Hit p _ == Hit q _ = p == q
+instance Ord Hit where compare (Hit p _) (Hit q _) = compare p q
+
+points2 :: Int -> [Seg] -> [Hit]
+points2 _ [] = []
+points2 start (Seg pt dir n : segs) =
+    let delta = direction dir
+    in [Hit (add pt (scale k delta)) (start + k) | k <- [1..n]] ++ points2 (start + n) segs
+
 main :: IO ()
 main = do
     ls <- map (process (Pt 0 0) . parse) <$> getInput 3
     let pts = Set.toList (foldl1 Set.intersection (map (Set.fromList . concatMap points) ls))
     print (manhattan (head (sortOn manhattan pts)))
+
+    let idxMap1 = Map.fromList . reverse $ [(hitPt h, hitIdx h) | h <- points2 0 (ls !! 0)]
+        idxMap2 = Map.fromList . reverse $ [(hitPt h, hitIdx h) | h <- points2 0 (ls !! 1)]
+    print $ minimum (zipWith (+) (map (idxMap1 Map.!) pts) (map (idxMap2 Map.!) pts))