X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=src%2Ftask9%2Ftask9.hs;fp=src%2Ftask9%2Ftask9.hs;h=dac19e1b58951cd82ec61eff0d20816631ff4549;hb=e3a61aa8425c8ba085c567d04a23ba6146c2e04a;hp=0000000000000000000000000000000000000000;hpb=35fd88f4adee89988e8433c825f88b58a9691466;p=summerofcode2018soln.git

diff --git a/src/task9/task9.hs b/src/task9/task9.hs
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+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.List (inits, sortBy, foldl')
+import Data.Function (on)
+
+import Data.Text (Text)
+import qualified Data.Text.IO as TIO
+
+import Data.Void (Void)
+
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import qualified Text.Megaparsec.Char.Lexer as L
+import qualified Control.Applicative as CA
+
+import qualified Data.HashMap.Strict as M
+import Data.HashMap.Strict ((!))
+
+
+type Weight = Int
+type Value = Int
+data Bag = Bag { bagWeight :: Weight, bagValue :: Value} deriving (Show, Eq)
+data TableEntry = TableEntry {value :: Value, backpointer :: (Int, Weight)} deriving (Show, Eq)
+type DPTable = M.HashMap (Int, Weight) TableEntry
+
+main :: IO ()
+main = do 
+        bagsT <- TIO.readFile "data/09-bags.txt"
+        let bags = successfulParse bagsT
+        let limit = 5000
+        -- print bags
+        print $ part1 limit bags
+        print $ part2 limit bags
+
+part1 :: Weight -> [Bag] -> Int
+part1 limit bags = length $ last $ takeWhile (willFit limit) $ inits sortedBags
+    where sortedBags = sortBy (compare `on` bagWeight) bags
+          willFit limit' bags' = (sum $ map bagWeight bags') < limit'
+
+part2 :: Weight -> [Bag] -> Value
+part2 limit bags = value $ table!(length bags, limit)
+    where initialTable = M.fromList [((0, w), TableEntry {value = 0, backpointer = (0, w)}) | w <- [0..limit]]
+          table = foldl' includeBag initialTable 
+                          [ (thisBag, bagNumber, allowedWeight) 
+                          | (thisBag, bagNumber) <- zip bags [1..]
+                          , allowedWeight <- [0..limit]
+                          ]
+
+
+includeBag :: DPTable -> (Bag, Int, Weight) -> DPTable
+includeBag table (bag, bagNumber, weight) = 
+    if bagWeight bag > weight 
+    then M.insert here withoutBag table 
+    else if value withBagEntry + bagValue bag > value withoutBagEntry
+         then M.insert here withBag table
+         else M.insert here withoutBag table
+    where here = (bagNumber, weight)
+          withoutBagKey = (bagNumber - 1, weight)
+          withBagKey = (bagNumber - 1, weight - bagWeight bag)
+          withoutBagEntry = table!withoutBagKey
+          withBagEntry = table!withBagKey
+          withoutBag = TableEntry {value = value withoutBagEntry, backpointer = withoutBagKey}
+          withBag = TableEntry {value = value withBagEntry + bagValue bag, backpointer = withBagKey}
+
+
+-- Parse the input file
+
+type Parser = Parsec Void Text
+
+-- don't treat newlines as automatically-consumed whitespace
+sc :: Parser ()
+sc = L.space (skipSome (char ' ')) CA.empty CA.empty
+
+lexeme  = L.lexeme sc
+integer = lexeme L.decimal
+-- symb = L.symbol sc
+
+bagsFileP = bagP `sepBy` newline
+
+bagP = bagify <$> integer <*> integer
+    where bagify w v = Bag { bagWeight = w , bagValue = v}
+
+successfulParse :: Text -> [Bag]
+successfulParse input = 
+        case parse bagsFileP "input" input of
+                Left  _error -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
+                Right bags -> bags
\ No newline at end of file