#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

void solve() {
  int n; cin >> n;
  vector<int> p(n); REP(i, n) cin >> p[i], --p[i];
  vector<int> a;
  auto op = [&](int ai) -> void {
    a.emplace_back(ai);
    swap(p[ai], p[ai + 1]);
  };
  for (int i = 0; i < n;) {
    int j = i;
    while (j < n && p[j] != j) ++j;
    FOR(k, i, j) {
      if (p[k] < i || j <= p[k]) {
        cout << "-1\n";
        return;
      }
    }
    FOR(k, i, j) {
      for (int pos = (find(p.begin() + i, p.begin() + j, k) - p.begin()) - 1; pos >= k; --pos) {
        int l = pos;
        while (l >= k && p[l] == l + 1) --l;
        if (l < k) {
          for (; pos >= k; --pos) op(pos);
        } else {
          for (; l <= pos; ++l) op(l);
        }
      }
    }
    i = j + 1;
  }
  const int q = a.size();
  cout << q << '\n';
  REP(i, q) cout << a[i] + 1 << " \n"[i + 1 == q];
}

int main() {
  int t; cin >> t;
  while (t--) solve();
  return 0;
}