import java.io.PrintWriter
import scala.collection.mutable.*
import scala.io.StdIn.*
import scala.util.chaining.*
import scala.math.*
import scala.reflect.ClassTag
import scala.util.*
import scala.annotation.tailrec
import scala.collection.mutable


def solve(permutation: Array[Int]): Option[ArrayBuffer[Int]] =
  if permutation.forall(permutation.indices.contains(_)) then
    permutation.indices.find(i => permutation(i) == i) match
      case Some(i) =>
        solve(permutation.slice(0, i)).flatMap(result => solve(permutation.slice(i + 1, permutation.length).map(_ - i - 1)).map(_.map(_ + i + 1) ++ result))
      case None  =>
        Some(solveFlat(permutation))
  else
    None

def solveFlat(array: Array[Int]): ArrayBuffer[Int] =
  if array.isEmpty then
    return ArrayBuffer.empty
  val indices = Array.fill(array.length){0}
  val leftCount = Array.fill(array.length){0}
  for (a, i) <- array.zipWithIndex do
    indices(a) = i
    leftCount(a) = (0 until i).count(j => array(j) < array(i))
  val result = ArrayBuffer[Int]()
  val current = array.clone()
  def swap(i: Int) =
    if current(i) < current(i + 1) then
      leftCount(current(i + 1)) -= 1
    else
      leftCount(current(i)) += 1
    val temp = current(i)
    current(i) = current(i + 1)
    current(i + 1) = temp
    indices(current(i)) = i
    indices(current(i + 1)) = i + 1
    result.addOne(i + 1)
  for i <- array.indices do
    for j <- i until indices(i) do
      if current(j) != j + 1 && current(j + 1) == j + 2 && leftCount(j + 2) + 1 != j + 2 then
        swap(j)
    for j <- indices(i) until i by -1 do
      swap(j - 1)
  result


@main def main =
  val testCount = readLine().toInt
  for testCase <- 1 to testCount do
    val n = readLine().toInt
    val permutation = readLine().split(' ').map(_.toInt - 1)
    solve(permutation) match
      case Some(result) =>
        println(result.size)
        println(result.mkString(" "))
      case None =>
        println(-1)