From: Neil Smith <neil.git@njae.me.uk>
Date: Sun, 5 Dec 2021 11:27:18 +0000 (+0000)
Subject: Now using a delta to expand lines
X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;h=17e2b399ef252ee018f329462958047fb592ac22;p=advent-of-code-21.git

Now using a delta to expand lines
---

diff --git a/advent05/Main.hs b/advent05/Main.hs
index 2171ef7..5669a53 100644
--- a/advent05/Main.hs
+++ b/advent05/Main.hs
@@ -3,7 +3,7 @@
 import Data.Text ()
 import qualified Data.Text.IO as TIO
 
-import Data.Attoparsec.Text
+import Data.Attoparsec.Text hiding (take)
 import Control.Applicative
 
 import qualified Data.Map.Strict as M
@@ -23,22 +23,13 @@ main =
       print $ part1 trace
       print $ part2 trace
 
-part1 trace = M.size $ M.filter (> 1) diagramHV
-  where hLines = map expandLineH $ filter isHoriz trace
-        vLines = map expandLineV $ filter isVert  trace
-        diagramH = addLines M.empty hLines
-        diagramHV = addLines diagramH vLines
-
-part2 trace = M.size $ M.filter (> 1) diagram4
-  where hLines = map expandLineH $ filter isHoriz trace
-        vLines = map expandLineV $ filter isVert trace
-        pdLines = map expandLinePD $ filter isPDiag trace
-        ndLines = map expandLineND $ filter isNDiag trace
-        diagram1 = addLines M.empty hLines
-        diagram2 = addLines diagram1 vLines
-        diagram3 = addLines diagram2 pdLines
-        diagram4 = addLines diagram3 ndLines
+part1 trace = M.size $ M.filter (> 1) diagram
+  where hvLines = map expandLine $ filter isHorizOrVert trace
+        diagram = addLines M.empty hvLines
 
+part2 trace = M.size $ M.filter (> 1) diagram
+  where allLines = map expandLine trace
+        diagram = addLines M.empty allLines
 
 
 isHoriz :: Line -> Bool
@@ -47,61 +38,26 @@ isHoriz (Line (V2 x0 _y0) (V2 x1 _y1)) = x0 == x1
 isVert :: Line -> Bool
 isVert (Line (V2 _x0 y0) (V2 _x1 y1)) = y0 == y1
 
--- x and y increasing together
-isPDiag :: Line -> Bool
-isPDiag (Line (V2 x0 y0) (V2 x1 y1)) =
-  (x0 /= x1) 
-  && (y0 /= y1) 
-  && ((x1 - x0) == (y1 - y0))
-
--- x increasing, y decreasing
-isNDiag :: Line -> Bool
-isNDiag (Line (V2 x0 y0) (V2 x1 y1)) =
-  (x0 /= x1) 
-  && (y0 /= y1) 
-  && ((x1 - x0) == (y0 - y1))
-  
-
--- horizOrVert :: Line -> Bool
--- horizOrVert line = isHoriz line || isVert line
-
-
--- hovLines = filter horizOrVert
-
-expandLineH :: Line -> [Point]
-expandLineH (Line (V2 x0 y0) (V2 _x1 y1)) = -- x0 == x1
-  [V2 x0 y | y <- [yMin..yMax]]
-  where yMin = min y0 y1
-        yMax = max y0 y1
-
-expandLineV :: Line -> [Point]
-expandLineV (Line (V2 x0 y0) (V2 x1 _y1)) = -- y0 == y1
-  [V2 x y0 | x <- [xMin..xMax]]
-  where xMin = min x0 x1
-        xMax = max x0 x1
-
--- x and y increasing together
-expandLinePD :: Line -> [Point]
-expandLinePD (Line (V2 x0 y0) (V2 x1 y1)) = map (uncurry V2) coords
-  where xMin = min x0 x1
-        xMax = max x0 x1
-        yMin = min y0 y1
-        yMax = max y0 y1
-        coords = zip [xMin..xMax] [yMin..yMax]
-
--- x increasing, y decreasing
-expandLineND :: Line -> [Point]
-expandLineND (Line (V2 x0 y0) (V2 x1 y1)) = map (uncurry V2) coords
-  where xMin = min x0 x1
-        xMax = max x0 x1
-        yMin = min y0 y1
-        yMax = max y0 y1
-        yMax1 = yMax - 1
-        coords = zip [xMin..xMax] [yMax, yMax1..yMin]
+isHorizOrVert :: Line -> Bool
+isHorizOrVert line = (isHoriz line) || (isVert line)
+
+expandLine :: Line -> [Point]
+expandLine line@(Line p0 _p1) = take numPoints $ iterate (^+^ delta) p0
+  where numPoints = findLen line + 1
+        delta = findDelta line
+
+findLen :: Line -> Int
+findLen (Line (V2 x0 y0) (V2 x1 y1)) = 
+  max (abs (x1 - x0)) (abs (y1 - y0))
 
+findDelta :: Line -> Point
+findDelta (Line (V2 x0 y0) (V2 x1 y1)) = (V2 dx dy)
+  where dx = signum (x1 - x0)
+        dy = signum (y1 - y0)
 
 addLines :: Grid -> [[Point]] -> Grid
-addLines diagram expandedLines = foldr insertLine diagram expandedLines
+-- addLines diagram expandedLines = foldr insertLine diagram expandedLines
+addLines = foldr insertLine 
   where insertPoint p d = M.insertWith (+) p 1 d
         insertLine l d = foldr insertPoint d l