Time limit : 2sec / Memory limit : 256MB
The season for Snuke Festival has come again this year. First of all, Ringo will perform a ritual to summon Snuke. For the ritual, he needs an altar, which consists of three parts, one in each of the three categories: upper, middle and lower.
He has N parts for each of the three categories. The size of the i-th upper part is Ai, the size of the i-th middle part is Bi, and the size of the i-th lower part is Ci.
To build an altar, the size of the middle part must be strictly greater than that of the upper part, and the size of the lower part must be strictly greater than that of the middle part. On the other hand, any three parts that satisfy these conditions can be combined to form an altar.
How many different altars can Ringo build? Here, two altars are considered different when at least one of the three parts used is different.
All input values are integers.
Input is given from Standard Input in the following format:
A1 … AN
B1 … BN
C1 … CN
Print the number of different altars that Ringo can build.
2 1 5 2 4 3 6
3 1 1 1 2 2 2 3 3 3
6 3 14 159 2 6 53 58 9 79 323 84 6 2643 383 2 79 50 288
My solution as Time Limit Exceeded:
import qualified Data.Char as Char import qualified Data.List as List import qualified Data.Maybe as Maybe import qualified Text.Printf as Printf import qualified Control.Monad as Monad import qualified Data.Array as Array bisectLeft :: (Ord a) => a -> (Array.Array Int a) -> Int bisectLeft n xs = bisectLeft' 0 (length xs) n xs bisectLeft' :: (Ord a) => Int -> Int -> a -> (Array.Array Int a) -> Int bisectLeft' lo hi n xs = if lo >= hi then lo else if n <= (xs Array.! mid) then bisectLeft' lo mid n xs else bisectLeft' (mid + 1) hi n xs where mid = (lo + hi) `div` 2 bisectRight :: (Ord a) => a -> (Array.Array Int a) -> Int bisectRight n xs = bisectRight' 0 (length xs) n xs bisectRight' :: (Ord a) => Int -> Int -> a -> (Array.Array Int a) -> Int bisectRight' lo hi n xs = if lo >= hi then hi else if n < (xs Array.! mid) then bisectRight' lo mid n xs else bisectRight' (mid + 1) hi n xs where mid = (lo + hi) `div` 2 main :: IO () main = do n <- (read :: String -> Int) <$ > getLine as <- (Array.listArray (0,n-1)) . List.sort . map (read :: String -> Int) . words <$ > getLine bs <- map (read :: String -> Int) . words <$ > getLine cs <- (Array.listArray (0,n-1)) . List.sort . map (read :: String -> Int) . words <$ > getLine print $ foldl (+) 0 $ map (\ b -> (bisectLeft b as) * (n - bisectRight b cs)) bs
I think it takes too much time to make array, but I cannot think of any way to make it more efficient…
How can I this code more efficient?
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