{-# LANGUAGE BangPatterns #-} import System.Environment data Color = Red | Black data Tree α β = Leaf | Node Color (Tree α β) α β (Tree α β) fold :: (α -> β -> σ -> σ) -> Tree α β -> σ -> σ fold _ Leaf b = b fold f (Node _ l k v r) b = fold f r (f k v (fold f l b)) balance1 :: Tree α β -> Tree α β -> Tree α β balance1 (Node _ _ kv vv t) (Node _ (Node Red l kx vx r₁) ky vy r₂) = Node Red (Node Black l kx vx r₁) ky vy (Node Black r₂ kv vv t) balance1 (Node _ _ kv vv t) (Node _ l₁ ky vy (Node Red l₂ kx vx r)) = Node Red (Node Black l₁ ky vy l₂) kx vx (Node Black r kv vv t) balance1 (Node _ _ kv vv t) (Node _ l ky vy r) = Node Black (Node Red l ky vy r) kv vv t balance1 _ _ = Leaf balance2 :: Tree α β -> Tree α β -> Tree α β balance2 (Node _ t kv vv _) (Node _ (Node Red l kx₁ vx₁ r₁) ky vy r₂) = Node Red (Node Black t kv vv l) kx₁ vx₁ (Node Black r₁ ky vy r₂) balance2 (Node _ t kv vv _) (Node _ l₁ ky vy (Node Red l₂ kx₂ vx₂ r₂)) = Node Red (Node Black t kv vv l₁) ky vy (Node Black l₂ kx₂ vx₂ r₂) balance2 (Node _ t kv vv _) (Node _ l ky vy r) = Node Black t kv vv (Node Red l ky vy r) balance2 _ _ = Leaf is_red :: Tree α β -> Bool is_red (Node Red _ _ _ _) = True is_red _ = False lt x y = x < y ins :: Ord α => Tree α β -> α -> β -> Tree α β ins Leaf kx vx = Node Red Leaf kx vx Leaf ins (Node Red a ky vy b) kx vx = (if lt kx ky then Node Red (ins a kx vx) ky vy b else if lt ky kx then Node Red a ky vy (ins b kx vx) else Node Red a ky vy (ins b kx vx)) ins (Node Black a ky vy b) kx vx = if lt kx ky then (if is_red a then balance1 (Node Black Leaf ky vy b) (ins a kx vx) else Node Black (ins a kx vx) ky vy b) else if lt ky kx then (if is_red b then balance2 (Node Black a ky vy Leaf) (ins b kx vx) else Node Black a ky vy (ins b kx vx)) else Node Black a kx vx b set_black :: Tree α β -> Tree α β set_black (Node _ l k v r) = Node Black l k v r set_black e = e insert t k v = if is_red t then set_black (ins t k v) else ins t k v type Map = Tree Int Bool mk_Map_aux :: Int -> Int -> Map -> [Map] -> [Map] mk_Map_aux freq 0 m r = m:r mk_Map_aux freq n m r = let n' = n-1 in -- We try to stay away from language-specific optimizations, -- but in this instance strictness is imperative to ensure -- that `freq` is indeed respected instead of keeping all -- binary trees alive in thunks. let !m' = (insert m n' (n' `mod` 10 == 0)) in let !r' = if (n' `mod` freq == 0) then (m':r) else r in mk_Map_aux freq n' m' r' mk_Map n freq = mk_Map_aux freq n Leaf [] myLen :: [Map] -> Int -> Int myLen ((Node _ _ _ _ _) : xs) r = myLen xs (r+1) myLen (_ : xs) r = myLen xs r myLen [] r = r main = do [n, freq] <- getArgs let mList = mk_Map (read n) (read freq) let v = fold (\_ v r -> if v then r + 1 else r) (head mList) 0 :: Int print (show (myLen mList 0) ++ " " ++ show v)