From 51389d5cd4cba7f24464e200b363b16c81a78e9f Mon Sep 17 00:00:00 2001
From: Neil Smith <neil.git@njae.me.uk>
Date: Sat, 26 Dec 2020 11:03:37 +0000
Subject: [PATCH] Done part 1

---
 advent17/package.yaml    | 62 ++++++++++++++++++++++++++++++++++++++++
 advent17/src/advent17.hs | 51 +++++++++++++++++++++++++++++++++
 data/advent17.txt        |  8 ++++++
 data/advent17a.txt       |  3 ++
 stack.yaml               |  1 +
 5 files changed, 125 insertions(+)
 create mode 100644 advent17/package.yaml
 create mode 100644 advent17/src/advent17.hs
 create mode 100644 data/advent17.txt
 create mode 100644 data/advent17a.txt

diff --git a/advent17/package.yaml b/advent17/package.yaml
new file mode 100644
index 0000000..4d7792b
--- /dev/null
+++ b/advent17/package.yaml
@@ -0,0 +1,62 @@
+# This YAML file describes your package. Stack will automatically generate a
+# Cabal file when you run `stack build`. See the hpack website for help with
+# this file: <https://github.com/sol/hpack>.
+
+name: advent17
+synopsis: Advent of Code
+version: '0.0.1'
+
+default-extensions:
+- AllowAmbiguousTypes
+- ApplicativeDo
+- BangPatterns
+- BlockArguments
+- DataKinds
+- DeriveFoldable
+- DeriveFunctor
+- DeriveGeneric
+- DeriveTraversable
+- EmptyCase
+- FlexibleContexts
+- FlexibleInstances
+- FunctionalDependencies
+- GADTs
+- GeneralizedNewtypeDeriving
+- ImplicitParams
+- KindSignatures
+- LambdaCase
+- MonadComprehensions
+- MonoLocalBinds
+- MultiParamTypeClasses
+- MultiWayIf
+- NamedFieldPuns
+- NegativeLiterals
+- NumDecimals
+# - OverloadedLists
+- OverloadedStrings
+- PartialTypeSignatures
+- PatternGuards
+- PatternSynonyms
+- PolyKinds
+- RankNTypes
+- RecordWildCards
+- ScopedTypeVariables
+- TemplateHaskell
+- TransformListComp
+- TupleSections
+- TypeApplications
+- TypeFamilies
+- TypeInType
+- TypeOperators
+- ViewPatterns
+
+
+executables:
+  advent17:
+    main: advent17.hs
+    source-dirs: src
+    dependencies:
+    - base >= 2 && < 6
+    - containers
+    - linear
+    - vector
diff --git a/advent17/src/advent17.hs b/advent17/src/advent17.hs
new file mode 100644
index 0000000..535f971
--- /dev/null
+++ b/advent17/src/advent17.hs
@@ -0,0 +1,51 @@
+-- import Debug.Trace
+
+import qualified Data.Set as S
+import Linear (V3(..), V4(..), (^+^), (^-^))
+import qualified Data.Vector as V
+
+type Coord = V3 Int -- x, y, z
+type Grid = S.Set Coord
+
+main :: IO ()
+main = 
+    do grid0 <- readGrid "data/advent17.txt"
+       print grid0
+       let finalGrid = head $ drop 6 $ iterate update grid0
+       print $ S.size finalGrid
+
+
+readGrid :: String -> IO Grid
+readGrid filename = 
+    do  gs <- readFile filename
+        let grid = lines gs
+        let isActive x y = (grid!!y)!!x == '#'
+        let maxX = length (head grid) - 1
+        let maxY = length grid - 1
+        return $ S.fromList [ V3 x y 0 | x <- [0..maxX], y <- [0..maxY], isActive x y]
+
+neighbourSpaces :: Coord -> Grid
+neighbourSpaces here = S.map (here ^+^) nbrs
+  where nbrs = S.fromList [ V3 dx dy dz
+             | dx <- [-1, 0, 1]
+             , dy <- [-1, 0, 1]
+             , dz <- [-1, 0, 1]
+             , (dx, dy, dz) /= (0, 0, 0)]
+
+countOccupiedNeighbours :: Coord -> Grid -> Int
+countOccupiedNeighbours cell grid = S.size $ S.intersection grid $ neighbourSpaces cell
+
+cubeSurvives :: Grid -> Coord -> Bool
+cubeSurvives grid cell = alive && (nNbrs == 2 || nNbrs == 3)
+  where alive = cell `S.member` grid
+        nNbrs = countOccupiedNeighbours cell grid
+
+cubeBorn :: Grid -> Coord -> Bool
+cubeBorn grid cell = dead && (nNbrs == 3)
+  where dead = cell `S.notMember` grid
+        nNbrs = countOccupiedNeighbours cell grid
+
+update :: Grid -> Grid
+update grid = S.union (S.filter (cubeSurvives grid) grid) (S.filter (cubeBorn grid) empties)
+  where empties = (S.foldr mergeEmpties S.empty grid) `S.difference` grid
+        mergeEmpties cell acc = S.union acc $ neighbourSpaces cell
diff --git a/data/advent17.txt b/data/advent17.txt
new file mode 100644
index 0000000..9ebe8fa
--- /dev/null
+++ b/data/advent17.txt
@@ -0,0 +1,8 @@
+.###.#.#
+####.#.#
+#.....#.
+####....
+#...##.#
+########
+..#####.
+######.#
diff --git a/data/advent17a.txt b/data/advent17a.txt
new file mode 100644
index 0000000..eedd3d2
--- /dev/null
+++ b/data/advent17a.txt
@@ -0,0 +1,3 @@
+.#.
+..#
+###
diff --git a/stack.yaml b/stack.yaml
index 9e7091d..d9fee51 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -51,6 +51,7 @@ packages:
 - advent14
 - advent15
 - advent16
+- advent17
 
 # Dependency packages to be pulled from upstream that are not in the resolver.
 # These entries can reference officially published versions as well as
-- 
2.34.1