Data commit

Task/Happy-numbers/Haskell/happy-numbers-1.hs

@@ -0,0 +1,14 @@
+import Data.Char (digitToInt)
+import Data.Set (member, insert, empty)
+
+isHappy :: Integer -> Bool
+isHappy = p empty
+  where
+    p _ 1 = True
+    p s n
+      | n `member` s = False
+      | otherwise = p (insert n s) (f n)
+    f = sum . fmap ((^ 2) . toInteger . digitToInt) . show
+
+main :: IO ()
+main = mapM_ print $ take 8 $ filter isHappy [1 ..]

Task/Happy-numbers/Haskell/happy-numbers-2.hs

@@ -0,0 +1,19 @@
+import Data.Array (Array, (!), listArray)
+
+happy :: Int -> Bool
+happy x
+  | xx <= 150 = seen ! xx
+  | otherwise = happy xx
+  where
+    xx = dsum x
+    seen :: Array Int Bool
+    seen =
+      listArray (1, 150) $ True : False : False : False : (happy <$> [5 .. 150])
+    dsum n
+      | n < 10 = n * n
+      | otherwise =
+        let (q, r) = n `divMod` 10
+        in r * r + dsum q
+
+main :: IO ()
+main = print $ sum $ take 10000 $ filter happy [1 ..]