Problem 8

This problem actually wasn’t as bad as I originally thought it would be.

ProjectEuler8.hs
main :: IO ()
main = do
    putStrLn "ProjectEuler.net"
    putStrLn "Problem8 - Largest product in a series"
    print problem8

--Largest product in a series
problem8 = maximum listOfProducts

stringToList :: String -> [String]
stringToList n = map (\x -> [x] :: [Char]) n

listOfProducts = map product groupedInts

groupedInts = map (\x -> (take 13 (drop x listOfInts))) [0,1..(1000-13)]

listOfInts = map (read::String->Int) listOfStrings

listOfStrings = (stringToList largeString)

largeString = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450"

I’m sure that there are better ways to go about solving this problem. I know that the String data type is stored as a list of Char type, so I should have been able to convert immediately from String to [Int] with a map function. Unfortunately I wasn’t able to get this conversion to work so I had to take extra steps to convert the String to [String].

Once I had a list of Int it was rather straight forward to create groups of 13 integers and map product over them.