#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 1009;
int n, a[N], vis[N], fa[N], dep[N];
void work() {
    cin >> n;
    for(int i = 1; i < 2 * n; i ++) cin >> a[i];
   //a[1] = a[2 * n - 1] = 1;
    int l = 2 * n, r = 0;
    for(int i = 1; i < 2 * n; i ++) {
        if(a[i] == 0) {
            l = min(l, i);
            r = max(r, i);
        }
    }
    for(int i = 1; i <= n; i ++) dep[i] = vis[i] = fa[i] = 0;
    int now = 0;
    for(int i = 1; i < l; i ++) {
        if(vis[a[i]]) now = a[i];
        else fa[a[i]] = now, dep[a[i]] = dep[now] + 1, now = a[i];
        vis[a[i]] = 1;
    }
    set<int> s;
    for(int i = 1; i <= n; i ++) s.insert(i), vis[i] = 0;
    int Now = 0;
    for(int i = 2 * n - 1; i > r; i --) {
        if(vis[a[i]]) Now = a[i];
        else fa[a[i]] = Now, dep[a[i]] = dep[Now] + 1, Now = a[i];
        vis[a[i]] = 1;
    }
    for(int i = 1; i <= n; i ++)
        s.erase(a[i]);
    int num = r - l + 1;
    vector<int> a1, a2;
    int x = now, X = Now;
    //cout << x << " " << X << " " << dep[x] << " " << dep[X] << endl;
    while(x != X) {
        if(dep[x] >= dep[X]) {
            x = fa[x];
            if(x != X) a2.push_back(x);
        }
        else {
            X = fa[X];
            if(x != X) a2.push_back(X);
        }
        //cout << x << " " << X << endl;
    }
    if(now != Now)a2.push_back(Now);
    reverse(a2.begin(), a2.end());
    for(auto v : a2) a1.push_back(v);
    //for(auto v : a1) cout << v << " ";
    //cout << endl;

    reverse(a1.begin(), a1.end());

    for(int i = 1; i < l; i ++) cout << a[i] << " ";
    for(int i = l; i <= r; i ++) {
        if(!s.empty() && (a1.empty() || *s.begin() < a1.back())) {
            if(now)a1.push_back(now);
            now = *s.begin();
            s.erase(s.begin());
            cout << now << " ";
        } else {
            cout << a1.back() << " ";
            now = a1.back();
            a1.pop_back();
        }
    }
    for(int i = r + 1; i < 2 * n; i ++) cout << a[i] << " ";
    cout << endl;
}
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int Case;
    cin >> Case;
    while(Case --) work();
    return 0;
}