55 lines
1.4 KiB
Haskell
55 lines
1.4 KiB
Haskell
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import Data.List (nub)
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import Parsing (splitByString)
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main :: IO ()
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main = do
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input <- getContents
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let
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crabs = parseCrabs input
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(putStrLn . show . solution1) crabs
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(putStrLn . show . solution2) crabs
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solution1 :: [Int] -> Int
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solution1 = minFuel crabFuel1
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solution2 :: [Int] -> Int
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solution2 = minFuel crabFuel2
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parseCrabs :: String -> [Int]
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parseCrabs = (map read) . (splitByString ",")
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minFuel :: (Int -> Int -> Int) -> [Int] -> Int
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minFuel crabf crabs = minimum (map total positions)
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where
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uniqueCrabs = nub crabs
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positions = [minimum uniqueCrabs..maximum uniqueCrabs]
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total position = totalFuel crabf position crabs
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totalFuel :: (Int -> Int -> Int) -> Int -> [Int] -> Int
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totalFuel crabf position = sum . (map (crabf position))
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crabFuel1 :: Int -> Int -> Int
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crabFuel1 crab position = abs (crab - position)
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crabFuel2 :: Int -> Int -> Int
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crabFuel2 crab position =
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-- Just the sum of 1..<distance from crab to position>
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-- (using that Gauß-attributed sum)
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end * (end + 1) `quot` 2
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where
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end :: Int
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end = crabFuel1 crab position
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-- Tests
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testInput = "16,1,2,0,4,2,7,1,2,14"
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parsedInput = parseCrabs testInput
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test1 = solution1 parsedInput
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test2 = solution2 parsedInput
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testTotalFuel1 = totalFuel crabFuel1 2 parsedInput
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testTotalFuel2 = totalFuel crabFuel1 1 parsedInput
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testTotalFuel3 = totalFuel crabFuel1 3 parsedInput
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testTotalFuel4 = totalFuel crabFuel1 10 parsedInput
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