Project Euler 解答

Project Euler Problem 036

Project Euler Problem 036

import Control.Monad
import Data.Char

ispalin :: (Eq a, Num a) => [a] -> Bool
ispalin l@(x:_) = x/=0 && reverse l == l

num2b :: Integer -> [Integer]
num2b = reverse . imp where
  imp 0 = []
  imp n = rem n 2:imp(quot n 2)

an :: Integer -> [Integer]
an n = [x | x<-[1..n],ispalin $ num2b x,ispalin (map digitToInt $ show x)]

ans1 :: Integer
ans1 = sum $ an 1000000

-- コンパイルして0.6sec
-- 872187
main :: IO ()
main = print ans1

since 2013