Finished Problem 74; added alternate solution without Map just to compare runtimes

74.hs

@@ -18,7 +18,7 @@ type ChainMap = Map.Map Integer Integer
 initialMap :: ChainMap
 initialMap = Map.fromList [(169, 3), (363601, 3), (1454, 3),
                            (871, 2), (872, 2), (45361, 2), (45362, 2),
-                           (1, 1), (2, 1), (145, 1)]
+                           (1, 1), (2, 1), (145, 1), (40585, 1)]
 
 sumOfFactorialOfDigits :: Integer -> Integer
 sumOfFactorialOfDigits n = sum $ map (digitFactorial . fromIntegral . digitToInt) $ show n
@@ -35,5 +35,5 @@ numOfLoops :: Integer -> Integer -> (Integer, ChainMap)
 numOfLoops bound length = foldr (\n (num, oldMap) -> let (chainLength, newMap) = getChainLength n oldMap
                                                      in (num + if chainLength == length then 1 else 0, newMap)) (0, initialMap) [3..bound]
 
-main = print $ let (length, sizeMap) = numOfLoops 10000 60
+main = print $ let (length, sizeMap) = numOfLoops 1000000 60
                in length

74_alt.hs

@@ -0,0 +1,39 @@
+import Data.Char (digitToInt)
+
+digitFactorial :: Integer -> Integer
+digitFactorial n = case n of 
+    0 -> 1
+    1 -> 1
+    2 -> 2
+    3 -> 6
+    4 -> 24
+    5 -> 120
+    6 -> 720
+    7 -> 5040
+    8 -> 40320
+    9 -> 362880
+
+loops :: Integer -> Maybe Integer
+loops n 
+    | n `elem` [169, 363601, 1454] = Just 3
+    | n `elem` [871, 872, 45361, 45362] = Just 2
+    | n `elem` [1, 2, 145, 40585] = Just 1
+    | otherwise = Nothing
+
+sumOfFactorialOfDigits :: Integer -> Integer
+sumOfFactorialOfDigits n = sum $ map (digitFactorial . fromIntegral . digitToInt) $ show n
+
+getChainLength :: Integer -> Integer
+getChainLength n = getChainLengthRec n 1
+
+getChainLengthRec :: Integer -> Integer -> Integer
+getChainLengthRec n length = 
+    let next = sumOfFactorialOfDigits n
+    in case loops next of 
+        Just x -> length + x
+        Nothing -> getChainLengthRec next (length + 1)
+
+numOfLoops :: Integer -> Integer -> Integer
+numOfLoops bound length = foldr (\n num -> num + if getChainLength n == length then 1 else 0) 0 [3..bound]
+
+main = print $ numOfLoops 1000000 60