//g++ 2.cpp -std=c++14 -O2 -I .
#include <bits/stdc++.h>
using namespace std;

#include <atcoder/all>
using namespace atcoder;

using ll = long long;
using ld = long double;

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vld = vector<ld>;
using vvld = vector<vld>;

#define fi first
#define se second
#define pb push_back
#define pq_big(T) priority_queue<T,vector<T>,less<T>>
#define pq_small(T) priority_queue<T,vector<T>,greater<T>>
#define all(a) a.begin(),a.end()
#define rep(i,start,end) for(ll i=start;i<(ll)(end);i++)
#define per(i,start,end) for(ll i=start;i>=(ll)(end);i--)

void solve(){
  int n;
  cin>>n;
  vi a(n);
  vi where(n);
  rep(i,0,n){
    cin>>a[i];
    a[i]--;
    where[a[i]]=i;
  }

  int x=-1;
  rep(i,0,n){
    if(a[i]==i){
      rep(j,x+1,i){
        if(a[j]<x+1||i<a[j]){
          cout<<-1<<endl;
          return;
        }
      }
      x=i;
    }
  }

  vi op;

  per(i,n-1,0){
    
    while(a[i]!=i){
      int flg=-1,st=where[i];

      rep(j,st+1,i+1){
        if(a[j]!=j-1){
          flg=j;
          break;
        }
      }

      if(flg==-1){
        rep(j,st,i){
          op.pb(j+1);
          where[a[j]]=j+1;
          where[a[j+1]]=j;
          swap(a[j],a[j+1]);
        }
      }
      else{
        per(j,flg-1,st+1){
          op.pb(j+1);
          where[a[j]]=j+1;
          where[a[j+1]]=j;
          swap(a[j],a[j+1]);
        }
        
        rep(j,st,flg){
          op.pb(j+1);
          where[a[j]]=j+1;
          where[a[j+1]]=j;
          swap(a[j],a[j+1]);
        }
      }
      
      
    }
  }

  cout<<op.size()<<endl;
  for(int a:op){
    cout<<a<<" ";
  }
  cout<<endl;
  return;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int t;
  cin>>t;

  while(t--){
    solve();
  }
}