Improve performance

.gitignore

@@ -1 +1,7 @@
+# Ignore everything without extension
+*
+!*/
+
 *.in
+*.hi
+*.o

Day1A.hs

@@ -1,6 +1,6 @@
 module Day1A where
 
-read' :: String -> Integer
+read' :: String -> Int
 read' ('+':str) = read str
 read' str = read str
 

Day1B.hs

@@ -1,14 +1,15 @@
 module Day1B where
 
 import Day1A (read')
-import qualified Data.Set as S
+import qualified Data.IntSet as S
 
-handle :: Integer -> (S.Set Integer) -> [Integer] -> Integer
+handle :: Int -> S.IntSet -> [Int] -> Int
 handle freq history (nextDelta:xs)
-  | S.member freq history = freq  -- When the frequency is in the history set, return it
-  | otherwise             = handle (freq + nextDelta) (S.insert freq history) xs  -- Recurse otherwise
+  | (S.size s) == (S.size history) = freq  -- When the frequency is in the history set, return it
+  | otherwise                      = handle (freq + nextDelta) (S.insert freq history) xs  -- Recurse otherwise
+  where s = S.insert freq history
 handle _ _ _ = error "xs should not be empty :("
 
 main :: IO ()
 main = interact $ show . handle 0 S.empty . deltaFreqs
-  where deltaFreqs = cycle . map read' . lines  -- Convert input to Integers and repeat infinitely
+  where deltaFreqs = cycle . map read' . lines  -- Convert input to Ints and repeat infinitely