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On the Project Euler Forum I found the following solution for Problem 127, posted there by glguy.
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On the Project Euler Forum I found the following solution for Problem 127, posted there by glguy.<BR>
 
main = print $ solve 99999
 
main = print $ solve 99999
 
 

Revision as of 14:33, 25 February 2008

On the Project Euler Forum I found the following solution for Problem 127, posted there by glguy.
main = print $ solve 99999

rad x = fromIntegral $ product $ map fst $ primePowerFactors $ fromIntegral x

solve :: Int -> Int solve n = sum [ c | (rc,c) <- invrads

                 , 2 * rc < c
                 , (ra, a) <- takeWhile (\(a,_)->(c > 2*rc*a)) invrads
                 , a < c `div` 2
                 , gcd ra rc == 1
                 , ra * rads ! (c - a) < c `div` rc]
   where
    rads :: UArray Int Int
    rads = listArray (1,n) $ map rad [1..n]
    invrads = sort $ map (\(a,b) -> (b, a)) $ assocs rads

Would responsible people be so kind as to check copyvio for this one? hk