hi ,all : I'm a learn haskell couple of days , and I want to solve some problem [http://codeforces.com/contest/194/problem/D] with haskell , I know the algorithm for the problem and implement it with haskell , but i jsut get TLE on the test case . Here is my code , how i can implement it more Efficient ? code : import Data.Bits import Data.Int --import Debug.Trace calc :: [Int64] -> [Int64] -> Int64 calc a b = sum $ zipWith (*) a b -- a p r fun2op :: [Int64] -> [Int] -> Int64 -> [Int64] --fun2op a x r | -- trace ("fun2op " ++ show a ++ " " ++ show x ++ " " ++ show r ) False = undefined fun2op _ [] _ = [] fun2op a (x:xs) r = (( a !! (x-1)) + r) : (fun2op a xs r ) gor :: [Int64] -> [Int64] -> Int -> Int -> Int64 -> Int64 gor a k dep u ans | ( ( u - dep ) .&. 1 :: Int) == 0 = max ans $ calc a k | otherwise = ans -- a , b , p , k , r , u , last , dep , ans dfs :: [Int64] -> [Int64] -> [Int] -> [Int64] -> Int64 -> Int -> Int -> Int -> Int64 -> Int64 dfs a b p k r u l dep ans -- | trace ("dfs " ++ show a ++ " " ++ show l ++ " " ++ show dep ++ " " ++ show ans) False = undefined | dep == u = max ans $ calc a k | l == 1 = df1 | otherwise = max (df1) ( dfs (zipWith ( xor ) a b ) b p k r u 1 (dep+1) tmpans) where pa = fun2op a p r tmpans = gor a k dep u ans df1 = dfs pa b p k r u 2 (dep + 1) tmpans rInt64 :: String -> Int64 rInt64 = read rInt :: String -> Int rInt = read main = do ss <- getLine let tmp = words ss let u = rInt (tmp !! 1) let r = rInt64 ( tmp !! 2) let x = map (rInt) $ words ss let x = map (rInt) $ words ss aa <- getLine let a = map (rInt64) $ words aa bb <- getLine let b = map (rInt64) $ words bb kk <- getLine let k = map (rInt64) $ words kk pp <- getLine let p = map (rInt) $ words pp print ( dfs a b p k r u 0 0 (rInt64 "-1000000000000000000")) -------------- Best Regards GTALK: ivoryxiong AT gmail.com