From 6723ef2021fb2cf2d7bcd97096b13c71adce203f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tristan=20Dani=C3=ABl=20Maat?= <tm@tlater.net>
Date: Tue, 14 Dec 2021 00:40:52 +0000
Subject: [PATCH] day11: Complete puzzles

---
 11/input.txt    | 10 ++++++
 11/octoflash.hs | 93 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 11/input.txt
 create mode 100644 11/octoflash.hs

diff --git a/11/input.txt b/11/input.txt
new file mode 100644
index 0000000..cfbdc33
--- /dev/null
+++ b/11/input.txt
@@ -0,0 +1,10 @@
+5421451741
+3877321568
+7583273864
+3451717778
+2651615156
+6377167526
+5182852831
+4766856676
+3437187583
+3633371586
diff --git a/11/octoflash.hs b/11/octoflash.hs
new file mode 100644
index 0000000..eb16571
--- /dev/null
+++ b/11/octoflash.hs
@@ -0,0 +1,93 @@
+import           Data.Char   (digitToInt)
+
+main :: IO ()
+main = do
+  input <- getContents
+  let
+    octopodes = (map (map digitToInt) . lines) input
+  (putStrLn . show . solution1) octopodes
+  (putStrLn . show . solution2) octopodes
+
+solution1 :: [[Int]] -> Int
+solution1 m = snd (iterate flashSimulate (m, 0) !! 100)
+
+solution2 :: [[Int]] -> Int
+solution2 m = countUntil (all (all (==0)) . fst) flashSimulate (m, 0)
+
+flashSimulate :: ([[Int]], Int) -> ([[Int]], Int)
+flashSimulate (octopodes, flashes) =
+  (refreshOctopodes exhaustedOctopodes, flashes + countExhaustedOctopodes exhaustedOctopodes)
+  where
+    exhaustedOctopodes = flashStep octopodes
+    countExhaustedOctopodes = foldr (\l a -> length l + a) 0 . map (filter (> 9))
+    refreshOctopodes = map (map (\o -> if o > 9 then 0 else o))
+
+flashStep :: [[Int]] -> [[Int]]
+flashStep = propagateFlashes . map (map (+1))
+  where
+    propagateFlashes :: [[Int]] -> [[Int]]
+    propagateFlashes = until allExhausted flashOctopi
+      where
+        allExhausted :: [[Int]] -> Bool
+        allExhausted = all (all (/= 10))
+        flashOctopi :: [[Int]] -> [[Int]]
+        flashOctopi m = map (map (incrementFlashing m))
+          [[(x, y) | y <- [0..length (m !! x) - 1]] | x <- [0..length m - 1]]
+          where
+            incrementFlashing ::[[Int]] -> (Int, Int) -> Int
+            incrementFlashing m' o
+              | charge < 10 && newCharge > 10 = 10 -- Ensure we don't miss an increment
+              | otherwise = charge + numFlashingNeighbors o
+              where
+                newCharge = charge + numFlashingNeighbors o
+                charge = m' !!! o
+            numFlashingNeighbors :: (Int, Int) -> Int
+            numFlashingNeighbors = length . filter (\o -> (m !!! o) == 10) . (flip adjacent m)
+
+(!!!) :: [[Int]] -> (Int, Int) -> Int
+(!!!) m index = m !! (fst index) !! (snd index)
+
+countUntil :: (a -> Bool) -> (a -> a) -> a -> Int
+countUntil p f = call
+  where
+    call x
+      | p x = 0
+      | otherwise = call (f x) + 1
+
+adjacent :: (Int, Int) -> [[Int]] -> [(Int, Int)]
+adjacent (x, y) m = [(x+i, y+j) |
+                     i <- [-1..1],
+                     j <- [-1..1],
+                     -- (i, j) /= (0, 0),
+                     x+i >= 0,
+                     y+j >= 0,
+                     x+i < length m,
+                     y+j < length (m !! 0)]
+
+-- Tests
+
+testInput1 = [
+  "5483143223",
+  "2745854711",
+  "5264556173",
+  "6141336146",
+  "6357385478",
+  "4167524645",
+  "2176841721",
+  "6882881134",
+  "4846848554",
+  "5283751526"
+  ]
+parsedTestInput1 = map (map digitToInt) testInput1
+
+testInput2 = [
+  "11111",
+  "19991",
+  "19191",
+  "19991",
+  "11111"
+  ]
+parsedTestInput2 = map (map digitToInt) testInput2
+
+test1 = solution1 parsedTestInput1
+test2 = solution2 parsedTestInput1