Day 11

advent-of-code-2023.cabal

@@ -84,3 +84,11 @@ executable day10
     build-depends:    base ^>=4.15.1.0, array
     hs-source-dirs:   day10
     default-language: Haskell2010
+
+executable day11
+    main-is:          Main.hs
+    other-modules:    Commons Part1 Part2
+
+    build-depends:    base ^>=4.15.1.0, array, Unique
+    hs-source-dirs:   day11
+    default-language: Haskell2010

day11/Commons.hs

@@ -0,0 +1,46 @@
+module Commons where
+
+import GHC.IO.Handle (isEOF)
+import Data.Array (Array, listArray, (!), indices)
+import Data.List.Unique (sortUniq)
+
+
+type Image = [(Int, Int)]
+type ExpansionArray = Array Int Int
+
+
+parseLine :: Int -> Int -> String -> Image
+parseLine _ _ [] = []
+parseLine row column ('#': t) = (column, row): parseLine row (column + 1) t
+parseLine row column (_: t) = parseLine row (column + 1) t
+
+parseImage :: Int -> Image -> IO Image
+parseImage row image = do done <- isEOF
+                          if done
+                             then return image
+                             else do line <- getLine
+                                     parseImage (row + 1) (image ++ parseLine row 1 line)
+
+parse :: IO Image
+parse = parseImage 1 []
+
+
+getExpansionArray :: Int -> Int -> Int -> [Int] -> [Int]
+getExpansionArray _ _ _ [] = []
+getExpansionArray i expOffset expInc (h: t)
+  | i == h = i + expOffset: getExpansionArray (i + 1) expOffset expInc t
+  | i < h  = i + expOffset: getExpansionArray (i + 1) (expOffset + expInc) expInc (h: t)
+
+getExpansionArrays :: Int -> Image -> (ExpansionArray, ExpansionArray)
+getExpansionArrays expInc image = let expX = getExpansionArray 1 0 expInc $ sortUniq . map fst $ image
+                                      expY = getExpansionArray 1 0 expInc $ sortUniq . map snd $ image
+                           in (listArray (1, length expX) expX, listArray (1, length expY) expY)
+
+getDistancesGalaxy :: Image -> (ExpansionArray, ExpansionArray) -> (Int, Int) -> [Int]
+getDistancesGalaxy [] _ _ = []
+getDistancesGalaxy ((x0, y0): t) (expX, expY) (x1, y1) =
+  abs ((expX ! x0) - (expX ! x1)) + abs ((expY ! y0) - (expY ! y1)): getDistancesGalaxy t (expX, expY) (x1, y1)
+
+getDistances :: Image -> (ExpansionArray, ExpansionArray) -> [[Int]]
+getDistances [] _ = []
+getDistances (h: t) (expX, expY) = getDistancesGalaxy t (expX, expY) h: getDistances t (expX, expY)

day11/Main.hs

@@ -0,0 +1,12 @@
+module Main where
+
+import Commons
+import qualified Part1
+import qualified Part2
+
+
+main = do image <- parse
+          let part1Res = sum . concat $ Part1.computeDistances image
+          print part1Res
+          let part2Res = sum . concat $ Part2.computeDistances image
+          print part2Res

day11/Part1.hs

@@ -0,0 +1,8 @@
+module Part1 where
+
+import Commons
+
+
+computeDistances :: Image -> [[Int]]
+computeDistances image = let expansionArrays = getExpansionArrays 1 image
+                         in getDistances image expansionArrays

day11/Part2.hs

@@ -0,0 +1,8 @@
+module Part2 where
+
+import Commons
+
+
+computeDistances :: Image -> [[Int]]
+computeDistances image = let expansionArrays = getExpansionArrays 999999 image
+                         in getDistances image expansionArrays