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mikamix/euler12.hs

Last active January 2, 2016 01:59
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euler12.hs
import Data.List
main = print $ head $ filter ((> 500) . countDivisors) triangleNumbers
triangleNumbers = scanl1 (+) [1..]
countDivisors n = product $ map ((+1) . length) (group (primeFactors n))
primeFactors n = primeFactors' n 2
where
primeFactors' n f
| f ^ 2 > n = [n]
| n `mod` f == 0 = f : primeFactors' (n `div` f) f
| otherwise = primeFactors' n (f + 1)
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