FilterElems.hs

module FilterElems where
import Data.List
import Control.Monad

-- abstract tuple comparison
sortTup f =
  case ord of
    EQ -> snd f
    _  -> ord
  where ord = fst f

sortFst (a1,a2) (b1,b2) = sortTup ((compare a1 b1), (compare a2 b2))
sortSnd (a1,a2) (b1,b2) = sortTup ((compare a2 b2), (compare a1 b1))
eqSnd (_, x) (_, y) = x == y

minI = minimum . map fst
minIndex xs@(x:_) = (minI xs, snd x)

(|>) = flip ($)
infixl 0 |>

findReps k xs =
  let xs' = xs |> zip [1..]
               |> sortBy sortSnd
               |> groupBy eqSnd
               |> filter ((>= k) . length)
  in case xs' of
    [] -> [-1]
    _  -> xs' |> map minIndex
              |> sortBy sortFst
              |> map snd

readIntList :: IO [Int]
readIntList = liftM (map read . words) getLine

main :: IO ()
main = do
  t <- readLn
  replicateM_ t $ do
    [_,k] <- readIntList
    as <- readIntList
    let ans = findReps k as
    putStrLn $ intercalate " " (map show ans)