From 6b16d921543a62d880171791d39bcc58560785fa Mon Sep 17 00:00:00 2001 From: Charles Date: Sun, 11 Aug 2019 22:36:40 +0200 Subject: haskell problems 001 -> 006 --- haskell/004-largest_palindrome_product.hs | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) create mode 100644 haskell/004-largest_palindrome_product.hs (limited to 'haskell/004-largest_palindrome_product.hs') diff --git a/haskell/004-largest_palindrome_product.hs b/haskell/004-largest_palindrome_product.hs new file mode 100644 index 0000000..e0bd77d --- /dev/null +++ b/haskell/004-largest_palindrome_product.hs @@ -0,0 +1,18 @@ +-- Largest palindrome product + +-- Problem 4 +-- A palindromic number reads the same both ways. +-- The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99. + +-- Find the largest palindrome made from the product of two 3-digit numbers. + + +main = do + print (maximum [x * y | x <- [0..999], y <- [0..999], is_palindrome (x * y)]) + +is_palindrome :: Int -> Bool +is_palindrome x = all (\(y, z) -> y == z) $ zip (show x) (rev' $ show x) + +rev' :: [a] -> [a] +rev' [] = [] +rev' (x:xs) = (rev' xs) ++ [x] -- cgit