#include <bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define all(x) x.begin(), x.end()

using namespace std;
template <class X, class Y> bool minimize(X &a, Y b) {
    if (a > b) return a = b, true;
    return false;
}
template <class X, class Y> bool maximize(X &a, Y b) {
    if (a < b) return a = b, true;
    return false;
}

const int N = 300005;
int a[2 * N];

void run_case() {
    int n; cin >> n;
    int m = 2 * n - 1;
    vector<bool> flag(n + 1, false);
    vector<int> par(n + 1, 0);
    vector<int> nxt(n + 1, 0);
    for (int i = 1; i <= m; i++) {
        cin >> a[i];
        flag[a[i]] = true;
    }
    if (n == 1) {
        cout << "1\n";
        return;
    }
    a[1] = a[m] = 1;
    flag[1] = 1;
    int pos[2];
    for (int iter = 0; iter < 2; ++iter) {
        for (int i = 1; i <= m; i++) {
            if (a[i + 1] == 0) {
                pos[iter] = i;
                break;
            }
        }
        map<pair<int, int>, bool> MP;
        for (int i = 1; i <= m; i++) {
            if (a[i + 1] == 0) {
                break;
            }
            int u = a[i];
            int v = a[i + 1];
            if (MP.find(mp(u, v)) != MP.end()) {
                continue;
            }
            par[v] = u;
            MP[mp(u, v)] = MP[mp(v, u)] = true;
        }
        reverse(a + 1, a + m + 1);
    }
    pos[1] = m - pos[1] + 1;
    pair<int, int> p(1, 1);
    vector<int> l(n + 1, 0);
    map<int, int> MP;
    for (int i = m; i >= 1; --i) {
        if (a[i] == 0) break;
        MP[a[i]] = i;
    }
    for (int i = 1; i <= m; ++i) {
        if (a[i] == 0) break;
        if (MP.count(a[i])) {
            p = {i, MP[a[i]]};
        }
    }
    vector<int> node, not_in;
    for (int i = 1; i <= n; i++) {
        if (!flag[i]) {
            not_in.push_back(i);
        }
    }
    sort(all(not_in), greater<int>());
    for (int u = a[pos[0]]; u != a[p.fi]; u = par[u]) {
        node.push_back(u);
    }
    node.push_back(a[p.fi]);
    int tmp = node.size();
    for (int u = a[pos[1]]; u != a[p.fi]; u = par[u]) {
        node.push_back(u);
    }
    if (node.begin() + tmp != node.end()) {
        reverse(node.begin() + tmp, node.end());
    }
    for (int i = 0; i + 1 < (int) node.size(); i++) {
        nxt[node[i]] = node[i + 1];
    }
    nxt[node.back()] = -1;
    int cur = node[0];
    vector<int> res;
    // cerr << "##\n" << '\n'; 
    // for (int x: node) {
    //     cerr << x << ' ';
    // }
    // cout << '\n';
    while (true) {
        if (nxt[cur] > 0) {
            int tmp = nxt[cur];
            if (!not_in.empty() && not_in.back() < tmp) {
                res.push_back(not_in.back());
                par[not_in.back()] = cur;
                not_in.pop_back();
                cur = res.back();
                continue;
            } 
            cur = tmp;
            res.push_back(cur);
            continue;
        }   
        if (nxt[cur] == 0) {
            int tmp = par[cur];
            if (!not_in.empty() && not_in.back() < tmp) {
                res.push_back(not_in.back());
                par[not_in.back()] = cur;
                not_in.pop_back();
                cur = res.back();
                continue;
            } 
            cur = tmp;
            res.push_back(cur);
            continue;
        }
        if (not_in.empty()) {
            break;
        }
        res.push_back(not_in.back());
        par[not_in.back()] = cur;
        cur = not_in.back();
        not_in.pop_back();
    }
    // for (int x: res) cerr << x << ' ';
    // cerr << "#####\n";
    for (int i = 1, t = 0; i <= m; i++) {
        if (a[i] == 0) {
            if (t == 0) {
                for (int x: res) {
                    cout << x << ' ';
                }
                t = 1;
            }
            continue;
        }
        if (i != pos[1]) cout << a[i] << ' ';
    }
    cout << '\n';
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    int t; cin >> t;
    while (t --) {
        run_case();
    }
    return 0;
}