結果

問題 No.1279 Array Battle
コンテスト
ユーザー こまる
提出日時 2020-11-18 17:50:25
言語 Haskell
(9.10.1)
結果
AC  
実行時間 894 ms / 2,000 ms
コード長 3,644 bytes
コンパイル時間 3,851 ms
コンパイル使用メモリ 248,672 KB
実行使用メモリ 8,704 KB
最終ジャッジ日時 2024-07-23 09:08:09
合計ジャッジ時間 9,152 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge2
このコードへのチャレンジ
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ファイルパターン 結果
other AC * 20
権限があれば一括ダウンロードができます
コンパイルメッセージ
Loaded package environment from /home/judge/.ghc/x86_64-linux-9.8.2/environments/default
[1 of 2] Compiling Main             ( Main.hs, Main.o )
[2 of 2] Linking a.out

ソースコード

diff # 

{-# LANGUAGE BangPatterns      #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TupleSections     #-}

import           Control.Monad
import           Control.Monad.Fix
import           Control.Monad.ST
import           Control.Monad.State
import           Data.Char
import           Data.Coerce
import           Data.IORef
import           Data.Ord
import qualified Data.ByteString.Char8             as BSC8
import qualified Data.Vector.Fusion.Stream.Monadic as VFSM
import qualified Data.Vector.Generic               as VG
import qualified Data.Vector.Generic.Mutable       as VGM
import qualified Data.Vector.Unboxed               as VU
import qualified Data.Vector.Unboxed.Mutable       as VUM

main :: IO ()
main = do
  n <- readLn :: IO Int
  a <- quickSort <$> seqInput n
  b <- quickSortBy (comparing Down) <$> seqInput n
  p <- VU.unsafeThaw $ VU.fromList ([0..(n - 1)] :: [Int])
  ans <- newIORef (0 :: Int)
  let res = VU.sum $ VU.zipWith (\x y -> max 0 (x - y)) a b
  fix $ \loop -> do
    s <- newIORef (0 :: Int)
    rep n $ \i -> do
      pi <- VUM.unsafeRead p i
      modifyIORef' s (+ max 0 (a VU.! pi - b VU.! i))
    su <- readIORef s
    when (su == res) $ modifyIORef' ans succ
    check <- VUM.nextPermutation p
    when check loop
  print =<< readIORef ans

quickSort :: (Ord a, VG.Vector v a) => v a -> v a
quickSort = quickSortBy compare

quickSortBy :: VG.Vector v a => (a -> a -> Ordering) -> v a -> v a
quickSortBy cmp = VG.modify $ fix $ \loop vec ->
  when (VGM.length vec > 1) $ do
    pivot <- getMedian3Pivot cmp vec
    cut   <- pivotPartition cmp vec pivot
    loop (VGM.unsafeDrop cut vec)
    loop (VGM.unsafeTake cut vec)
{-# INLINE quickSortBy #-}

pivotPartition :: (VGM.MVector mv a) => (a -> a -> Ordering) -> mv s a -> a -> ST s Int
pivotPartition cmp vec pivot = fix `flip` 0 `flip` VGM.length vec $ \loop !l !r -> do
  !l' <- flip fix l $ \loopL !i -> do
    x   <- VGM.unsafeRead vec i
    case cmp x pivot of
      LT -> loopL (i + 1)
      _  -> return i
  !r' <- flip fix (r - 1) $ \loopR !i -> do
    x <- VGM.unsafeRead vec i
    case cmp pivot x of
      LT -> loopR (i - 1)
      _  -> return i
  if l' < r'
    then do
      VGM.unsafeSwap vec l' r'
      loop (l' + 1) r'
    else return l'
{-# INLINE pivotPartition #-}

getMedian3Pivot :: (VGM.MVector mv a) => (a -> a -> Ordering) -> mv s a -> ST s a
getMedian3Pivot cmp vec = median cmp <$> VGM.unsafeRead vec 0 <*> VGM.unsafeRead vec (VGM.length vec `quot` 2) <*> VGM.unsafeRead vec (VGM.length vec - 1)
{-# INLINE getMedian3Pivot #-}

median :: (a -> a -> Ordering) -> a -> a -> a -> a
median cmp x y z = case cmp x y of
  LT -> case cmp y z of
    LT -> y
    _  -> case cmp x z of
      LT -> z
      _  -> x
  _  -> case cmp x z of
    LT -> x
    _  -> case cmp y z of
      LT -> z
      _  -> y
{-# INLINE median #-}

-- | l -> x -> r, +d
stream :: Monad m => Int -> Int -> Int -> VFSM.Stream m Int
stream !l !r !d = VFSM.Stream step l
  where
    step x
      | x <= r    = return $ VFSM.Yield x (x + d)
      | otherwise = return VFSM.Done
    {-# INLINE [0] step #-}
{-# INLINE [1] stream #-}

-- | 0 <= x < n, interval = 1
rep :: Monad m => Int -> (Int -> m ()) -> m ()
rep n = flip VFSM.mapM_ (stream 0 (n - 1) 1)
{-# INLINE rep #-}

type CParser a = StateT BSC8.ByteString Maybe a
runCParser :: CParser a -> BSC8.ByteString -> Maybe (a, BSC8.ByteString)
runCParser = runStateT
{-# INLINE runCParser #-}
int :: CParser Int
int = coerce $ BSC8.readInt . BSC8.dropWhile isSpace
{-# INLINE int #-}
seqInput :: Int -> IO (VU.Vector Int)
seqInput n = VU.unfoldrN n (runCParser int) <$> BSC8.getLine
{-# INLINE seqInput #-}
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