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@@ -0,0 +1,58 @@
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+{-
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+The four adjacent digits in the 1000-digit number that have the greatest product are 9*9*8*9 = 5832.
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+
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+73167176531330624919225119674426574742355349194934
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+96983520312774506326239578318016984801869478851843
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+85861560789112949495459501737958331952853208805511
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+12540698747158523863050715693290963295227443043557
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+66896648950445244523161731856403098711121722383113
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+62229893423380308135336276614282806444486645238749
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+30358907296290491560440772390713810515859307960866
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+70172427121883998797908792274921901699720888093776
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+65727333001053367881220235421809751254540594752243
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+52584907711670556013604839586446706324415722155397
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+53697817977846174064955149290862569321978468622482
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+83972241375657056057490261407972968652414535100474
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+82166370484403199890008895243450658541227588666881
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+16427171479924442928230863465674813919123162824586
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+17866458359124566529476545682848912883142607690042
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+24219022671055626321111109370544217506941658960408
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+07198403850962455444362981230987879927244284909188
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+84580156166097919133875499200524063689912560717606
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+05886116467109405077541002256983155200055935729725
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+71636269561882670428252483600823257530420752963450
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+
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+Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?
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+-}
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+
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+import Data.Char (ord)
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+
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+ban :: [Char]
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+ban = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450"
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+
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+ban_size :: Int
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+ban_size = length ban
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+
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+slice_13 :: Int -> [Char]
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+slice_13 start = (take 13 (drop start ban))
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+
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+solution :: Int
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+solution = go' 0 0
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+ where
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+ limit :: Int
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+ limit = ban_size - 13
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+
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+ c2i :: Char -> Int
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+ c2i x = (ord x - ord '0')
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+
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+ mul :: [Int] -> Int
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+ mul list = foldl (\x y -> x*y) 1 list
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+
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+ go' :: Int -> Int -> Int
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+ go' index res
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+ | index == limit = res
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+ | otherwise = go' (index+1) (if val > res then val else res)
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+ where val = mul (map c2i (slice_13 index))
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+
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+main :: IO ()
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+main = putStrLn ("Solution: " ++ show solution)
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