Data commit

Task/Ruth-Aaron-numbers/Haskell/ruth-aaron-numbers.hs

@@ -0,0 +1,51 @@
+import qualified Data.Set as S
+import Data.List.Split ( chunksOf )
+
+divisors :: Int -> [Int]
+divisors n = [d | d <- [2 .. n] , mod n d == 0]
+
+--for obvious theoretical reasons the smallest divisor of a number bare 1
+--must be prime
+primeFactors :: Int -> [Int]
+primeFactors n = snd $ until ( (== 1) . fst ) step (n , [] )
+ where
+  step :: (Int , [Int] ) -> (Int , [Int] )
+  step (n , li) = ( div n h , li ++ [h] )
+   where
+    h :: Int
+    h = head $ divisors n
+
+primeDivisors :: Int -> [Int]
+primeDivisors n = S.toList $ S.fromList $ primeFactors n
+
+solution :: (Int -> [Int] ) -> [Int]
+solution f = snd $ until ( (== 30 ) . length . snd ) step ([2 , 3] , [] )
+ where
+  step :: ([Int] , [Int] ) -> ([Int] , [Int])
+  step ( neighbours , ranums ) =  ( map ( + 1 ) neighbours , if (sum $ f
+   $ head neighbours ) == (sum $ f $ last neighbours) then
+   ranums ++ [ head neighbours ] else ranums )
+
+formatNumber :: Int -> String -> String
+formatNumber width num
+   |width > l = replicate ( width -l ) ' ' ++ num
+   |width == l = num
+   |width < l = num
+    where
+     l = length num
+
+main :: IO ( )
+main = do
+   let ruth_aaron_pairs = solution primeFactors
+       maxlen = length $ show $ last ruth_aaron_pairs
+       numberlines = chunksOf 8 $ map show ruth_aaron_pairs
+       ruth_aaron_divisors = solution primeDivisors
+       maxlen2 = length $ show $ last ruth_aaron_divisors
+       numberlines2 = chunksOf 8 $ map show ruth_aaron_divisors
+       putStrLn "First 30 Ruth-Aaaron numbers ( factors ) :"
+   mapM_ (\nlin -> putStrLn $ foldl1 ( ++ ) $ map (\st -> formatNumber (maxlen + 2) st )
+    nlin ) numberlines
+   putStrLn " "
+   putStrLn "First 30 Ruth-Aaron numbers( divisors ):"
+   mapM_ (\nlin -> putStrLn $ foldl1 ( ++ ) $ map (\st -> formatNumber (maxlen2 + 2) st )
+    nlin ) numberlines2