From: Neil Smith <neil.git@njae.me.uk>
Date: Sun, 16 Dec 2018 16:11:32 +0000 (+0000)
Subject: Day 14
X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;h=92b8d2e9bb05d589a794e45bc52c63ec19fa1da0;p=advent-of-code-18.git

Day 14
---

diff --git a/src/advent14/advent14.hs b/src/advent14/advent14.hs
new file mode 100644
index 0000000..9a219e1
--- /dev/null
+++ b/src/advent14/advent14.hs
@@ -0,0 +1,56 @@
+import qualified Data.Sequence as Q
+import Data.Sequence ((<|), (|>))
+import Data.List
+import Data.Foldable (toList)
+
+type Recipes = Q.Seq Int
+data State = State Int Int Recipes deriving (Eq, Show)
+
+targetLength = 327901
+-- targetLength = 59414
+
+main :: IO ()
+main = do 
+    let state = State 0 1 (Q.fromList [3, 7])
+    putStrLn $ part1 state
+    print $ part2 state
+
+part1 :: State -> String
+part1 state0 = concatMap show $ toList $ Q.take 10 $ Q.drop targetLength recipes
+    where (State _ _ recipes) = last $ takeWhile unfinished1 $ states state0
+
+unfinished1 :: State -> Bool
+unfinished1 (State _ _ recipes) = (Q.length recipes) <= (targetLength + 10)
+
+part2 :: State -> Int
+part2 state0 = if (takeR (Q.length targetSeq) recipes) == targetSeq
+               then (Q.length recipes) - (Q.length targetSeq)
+               else (Q.length recipes) - (Q.length targetSeq) - 1
+-- recipes -- (Q.length recipes) - (Q.length targetSeq)
+
+    where (State _ _ recipes) = head $ dropWhile (unfinished2 targetSeq) $ states state0
+
+unfinished2 :: Recipes -> State -> Bool
+unfinished2 target (State _ _ recipes) = 
+    ((takeR (Q.length target) recipes) /= target)
+    && 
+    ((Q.take (Q.length target) (takeR (1 + Q.length target) recipes)) /= target)
+
+states :: State -> [State]
+states = iterate extend
+
+extend :: State -> State
+extend (State e1 e2 recipes) = State e1' e2' recipes'
+    where v1 = Q.index recipes e1
+          v2 = Q.index recipes e2
+          total = v1 + v2
+          recipes' = if total >= 10
+                     then recipes |> (total `div` 10) |> (total `mod` 10)
+                     else recipes |> total
+          e1' = (e1 + v1 + 1) `mod` (Q.length recipes')
+          e2' = (e2 + v2 + 1) `mod` (Q.length recipes')
+
+targetSeq :: Recipes
+targetSeq = Q.fromList $ map read $ map (take 1 . drop 1) $ map show $ show targetLength 
+
+takeR n s = Q.drop (Q.length s - n) s