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08.hs
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{- |
- Module : 08.hs
- Author : Clement Poh
-
- The four adjacent digits in the 1000-digit number that have the greatest
- product are 9 × 9 × 8 × 9 = 5832.
-
- 73167176531330624919225119674426574742355349194934
- 96983520312774506326239578318016984801869478851843
- 85861560789112949495459501737958331952853208805511
- 12540698747158523863050715693290963295227443043557
- 66896648950445244523161731856403098711121722383113
- 62229893423380308135336276614282806444486645238749
- 30358907296290491560440772390713810515859307960866
- 70172427121883998797908792274921901699720888093776
- 65727333001053367881220235421809751254540594752243
- 52584907711670556013604839586446706324415722155397
- 53697817977846174064955149290862569321978468622482
- 83972241375657056057490261407972968652414535100474
- 82166370484403199890008895243450658541227588666881
- 16427171479924442928230863465674813919123162824586
- 17866458359124566529476545682848912883142607690042
-
- Find the thirteen adjacent digits in the 1000-digit number that have the
- greatest product. What is the value of this product?
- -}
module Main where
import Data.Char (digitToInt)
input :: String
input = "73167176531330624919225119674426574742355349194934\
\96983520312774506326239578318016984801869478851843\
\85861560789112949495459501737958331952853208805511\
\12540698747158523863050715693290963295227443043557\
\66896648950445244523161731856403098711121722383113\
\62229893423380308135336276614282806444486645238749\
\30358907296290491560440772390713810515859307960866\
\70172427121883998797908792274921901699720888093776\
\65727333001053367881220235421809751254540594752243\
\52584907711670556013604839586446706324415722155397\
\53697817977846174064955149290862569321978468622482\
\83972241375657056057490261407972968652414535100474\
\82166370484403199890008895243450658541227588666881\
\16427171479924442928230863465674813919123162824586\
\17866458359124566529476545682848912883142607690042\
\24219022671055626321111109370544217506941658960408\
\07198403850962455444362981230987879927244284909188\
\84580156166097919133875499200524063689912560717606\
\05886116467109405077541002256983155200055935729725\
\71636269561882670428252483600823257530420752963450"
answer :: Int
answer = find 0 input
find :: Int -> String -> Int
find m [] = m
find m (x:xs)
| v > m = find v xs
| otherwise = find m xs
where v = val (take 13 (x:xs))
val :: String -> Int
val = product . map digitToInt