X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=advent15.hs;fp=advent15.hs;h=e3c97fb2cb92f263dd68e7c361ab70e4ee25ab2b;hb=a14889eed39a71079594da4f4fe1a20adea4df3a;hp=0000000000000000000000000000000000000000;hpb=5a91723e71215afc4c48e48f932e72a32e859094;p=advent-of-code-16.git

diff --git a/advent15.hs b/advent15.hs
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+++ b/advent15.hs
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+import Text.Parsec 
+import Text.ParserCombinators.Parsec.Number
+
+main :: IO ()
+main = do 
+    text <- readFile "advent15.txt" 
+    let disks = successfulParse $ parseIfile text
+    part1 disks
+    part2 disks
+
+part1 :: [[Int]] -> IO ()
+part1 disks = print $ head $ filter (canFall disks) [0..]
+
+part2 :: [[Int]] -> IO ()
+part2 disks = print $ head $ filter (canFall disks2) [0..5000000]
+    where disks2 = id $! map (take 5000000) $ disks ++ [drop 7 $ drop 0 $ cycle [0..(11-1)]]
+
+canFall :: [[Int]] -> Int -> Bool
+canFall ds i = all (\d -> (d!!i) == 0) ds
+
+
+instructionFile = instructionLine `endBy` newline 
+instructionLine = diskify <$> (string "Disc #" *> int) 
+                          <*> (string " has " *> int)
+                          <*> (string " positions; at time=0, it is at position " *> int)
+                          <*  (string ".")
+                    where diskify n size pos0 = drop n $ drop pos0 $ cycle [0..(size-1)]
+
+parseIfile :: String -> Either ParseError [[Int]]
+parseIfile input = parse instructionFile "(unknown)" input
+
+parseIline :: String -> Either ParseError [Int]
+parseIline input = parse instructionLine "(unknown)" input
+
+successfulParse :: Either ParseError [a] -> [a]
+successfulParse (Left _) = []
+successfulParse (Right a) = a