euler8.hs

-- Problem 8
-- The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.
-- Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. 
-- What is the value of this product?

import Data.Char

input = concat [
		"73167176531330624919225119674426574742355349194934",
		"96983520312774506326239578318016984801869478851843",
		"85861560789112949495459501737958331952853208805511",
		"12540698747158523863050715693290963295227443043557",
		"66896648950445244523161731856403098711121722383113",
		"62229893423380308135336276614282806444486645238749",
		"30358907296290491560440772390713810515859307960866",
		"70172427121883998797908792274921901699720888093776",
		"65727333001053367881220235421809751254540594752243",
		"52584907711670556013604839586446706324415722155397",
		"53697817977846174064955149290862569321978468622482",
		"83972241375657056057490261407972968652414535100474",
		"82166370484403199890008895243450658541227588666881",
		"16427171479924442928230863465674813919123162824586",
		"17866458359124566529476545682848912883142607690042",
		"24219022671055626321111109370544217506941658960408",
		"07198403850962455444362981230987879927244284909188",
		"84580156166097919133875499200524063689912560717606",
		"05886116467109405077541002256983155200055935729725",
		"71636269561882670428252483600823257530420752963450"
		]

numbers :: Int -> [Char] -> [String]
numbers digits input
	| length input  < digits = []
	| otherwise = take digits input:numbers digits (tail input)

digitProduct :: String -> Int
digitProduct str = product $ map digitToInt str

main = do
    let answer = maximum $ map digitProduct $ numbers 13 input
    putStrLn ("Answer: " ++ show answer)