Day 17 done

[advent-of-code-17.git] / src / advent17 / advent17.hs

diff --git a/src/advent17/advent17.hs b/src/advent17/advent17.hs
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+{-# LANGUAGE NegativeLiterals #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE NegativeLiterals #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE BangPatterns #-}
+
+-- import Prelude hiding ((++))
+import Data.Vector.Unboxed ((!))
+import qualified Data.Vector.Unboxed as V
+import Data.List (foldl')
+
+type RingBuffer = V.Vector Int
+
+initialStepSize :: Int
+initialStepSize = 366
+
+initialRingBuffer :: RingBuffer
+initialRingBuffer = V.singleton 0
+
+
+main :: IO ()
+main = do 
+        print $ part1 2017
+        -- print $ part2 50000000
+        print $ ith 2017 366
+        print $ oneth 50000000 366
+
+
+
+part1 :: Int -> Int
+part1 k = (!1) $ (iterate updateRingBuffer initialRingBuffer)!!k
+
+part2 :: Int -> Int
+part2 k = finalBuffer!targetLoc
+    where finalBuffer = (iterate updateRingBuffer initialRingBuffer)!!k
+          zeroLoc = V.head $ V.elemIndices 0 finalBuffer
+          targetLoc = (zeroLoc + 1) `rem` (V.length finalBuffer)
+
+updateRingBuffer :: RingBuffer -> RingBuffer
+updateRingBuffer buffer = buffer'
+    where nextPos = (initialStepSize + 1) `rem` V.length buffer
+          (start, end) = V.splitAt nextPos buffer
+          nextValue = V.length buffer
+          buffer' = V.cons nextValue $ (V.++) end start
+
+
+
+(%) = mod
+
+ith :: Int -> Int -> Int
+ith i steps =
+    let (position, list) = foldl' (\(currPos, currList) n -> 
+            let newPos  = (currPos + steps % n + 1) % n
+            in  (newPos, take newPos currList ++ [n] ++ drop newPos currList))
+            (0, [0]) [1..i]
+    in  list !! (position + 1)
+
+oneth :: Int -> Int -> Int
+oneth i steps =
+    snd $ foldl' (\(currPos, currOneth) n -> 
+        let !newPos = (currPos + steps % n + 1) % n
+        in  (newPos, if newPos == 0 then n else currOneth)) 
+        (0, 1) [1..i]
+
+-- main :: IO ()
+-- main = do
+--     print $ ith   2017     312
+--     print $ oneth 50000000 312
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