{-

- Solution to Project Euler problem 32

- Copyright (c) Project Nayuki. All rights reserved.

-

- https://www.nayuki.io/page/project-euler-solutions

- https://github.com/nayuki/Project-Euler-solutions

-}

import Data.List (sort)

import qualified EulerLib

main = putStrLn (show ans)

ans = sum [n | n <- [1..9999], hasPandigitalProduct n]

hasPandigitalProduct :: Int -> Bool

hasPandigitalProduct n = or [pandigital ((digits n) ++ (digits i) ++ (digits (div n i)))

| i <- [1..(EulerLib.sqrt n)+1], mod n i == 0]

digits :: Int -> [Int]

digits 0 = [0]

digits n = digits' n where

digits' 0 = []

digits' n = (digits' (div n 10)) ++ [mod n 10]

pandigital :: [Int] -> Bool

pandigital d = (sort d) == [1..9]