#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

template<typename T>
vector<vector<T>> vec2d(int n, int m, T v){
    return vector<vector<T>>(n, vector<T>(m, v));
}

template<typename T>
vector<vector<vector<T>>> vec3d(int n, int m, int k, T v){
    return vector<vector<vector<T>>>(n, vector<vector<T>>(m, vector<T>(k, v)));
}

template<typename T>
void print_vector(vector<T> v, char delimiter=' '){
    if(v.empty()) {
        cout << endl;
        return;
    }
    for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter;
    cout << v.back() << endl;
}

vector<int> sub_solve(vector<int> p){
    int n = p.size();
    for(int i = 0; i < n; i++) assert(p[i] != i);
    vector<int> ans;
    auto add_ans = [&](int i){
        ans.push_back(i);
        swap(p[i], p[i+1]);
    };
    for(int i = 0; i < n; i++){
        // print_vector(p);
        if(p[i] == i) continue;
        vector<bool> ok(n, true);
        int idx = -1;
        for(int j = 0; j < n; j++){
            if(p[j] == i) idx = j;
            if(p[j] == j+1) ok[j] = false;
        }
        bool find_ok = false;
        for(int j = i; j+1 < idx; j++){
            if(ok[j]) find_ok = true;
            if(find_ok && !ok[j+1]){
                add_ans(j);
            }
        }
        for(int j = idx-1; j >= i; j--) add_ans(j);
    }
    // print_vector(p);
    return ans;
}

void solve(){
    int n; cin >> n;
    vector<int> p(n);
    for(int i = 0; i < n; i++) {
        cin >> p[i];
        p[i]--;
    }
    vector<int> v;
    vector<int> ans;
    int sum_ok = 0;
    for(int i = 0; i < n; i++){
        if(i == p[i] || i+1 == n){
            if(i != p[i]) v.push_back(p[i]);
            int m = v.size();
            if(!v.empty()){
                int v_min = *min_element(v.begin(), v.end());
                for(int i = 0; i < m; i++){
                    v[i] -= sum_ok;
                    if(v[i] >= m){
                        cout << -1 << endl;
                        return;
                    }
                }
            }
            auto u = sub_solve(v);
            for(int j: u) ans.push_back(j+sum_ok);
            v.clear();
            sum_ok += m+1;
        }else{
            v.push_back(p[i]);
        }
    }
    cout << ans.size() << endl;
    for(int x: ans) cout << x+1 << ' ';
    cout << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int t; cin >> t;
    while(t--) solve();
}