chapter1-dropbox.hs

chapter1.hs

{-
Chapter 1

1. The product of the first two digits is 24.
2. The fourth digit is half of the second digit.
3. The sum of the last two digits is the same as the sum of the first and third digits.
4. The sum of all the digits is 26.
5. The second and third digits add up to the last digit.
-}

import Char (digitToInt)

intAt n num
	| n >= length (show num) = 0
	| otherwise = fromIntegral $ digitToInt ((show num) !! n)

rule1 n = intAt 0 n * intAt 1 n == 24
rule2 n = intAt 3 n * 2 == intAt 1 n
rule3 n = intAt 3 n + intAt 4 n == intAt 0 n + intAt 2 n
rule4 n = sum (map digitToInt (show n)) == 26
rule5 n = intAt 1 n + intAt 2 n == intAt 4 n

test input = rule1 input && rule2 input && rule3 input && rule4 input && rule5 input
answer = [x | x <- [0..100000], test x]

main = do
	putStrLn $ show answer