module TestData.ParenTree where import qualified Data.Vector.Unboxed as V parenTree :: Int -> (V.Vector Int, V.Vector Int) parenTree n = case go ([],[]) 0 (if even n then n else n+1) of (ls,rs) -> (V.fromListN (length ls) (reverse ls), V.fromListN (length rs) (reverse rs)) where go (ls,rs) i j = case j-i of 0 -> (ls,rs) 2 -> (ls',rs') d -> let k = ((d-2) `div` 4) * 2 in go (go (ls',rs') (i+1) (i+1+k)) (i+1+k) (j-1) where ls' = i:ls rs' = j-1:rs