#include<bits/stdc++.h>
#define F(i, a, b) for(int i = a; i <= b; i ++)
#define Fd(i, a, b) for(int i = a; i >= b; i --)
#define pii pair<int, int> 
#define fi first
#define se second
#define pb push_back
using namespace std;
const int N = 1e6 + 10;
const int inf = 1e7 + 2;
int n, a[N], fa[N], vst[N], now[N];
vector<int> son[N];
void sol() {
    cin >> n;
    F(i, 1, 2 * n - 1) cin >> a[i];
    a[1] = a[2 * n - 1] = 1;
    F(i, 1, n) fa[i] = vst[i] = now[i] = 0;
    F(i, 1, n) son[i].clear();
    vst[1] = 3;
    int pos = 0;
    F(i, 2, 2 * n - 1) {
        if(a[i] == 0) {
            pos = i; 
            break;
        }
        if(! vst[a[i]]) vst[a[i]] = 1, fa[a[i]] = a[i - 1];
        else if(fa[a[i - 1]] == a[i]) vst[a[i - 1]] = 3;
    }
    Fd(i, 2 * n - 2, 2) {
        if(a[i] == 0) break;
        if(vst[a[i]] == 0) vst[a[i]] = 2, fa[a[i]] = a[i + 1];
        if(vst[a[i]] == 2) {
            if(fa[a[i]] == a[i - 1]) vst[a[i]] = 3;
        }
        if(vst[a[i]] == 1) {
            if(fa[a[i]] == a[i + 1]) vst[a[i]] = 3;
        }
    }
    // F(i, 1, n) cout << fa[i] << " \n" [i == n];
    // F(i, 1, n) cout << vst[i] << " \n" [i == n];
    priority_queue<int, vector<int>, greater<int> > q;
    F(i, 1, n) {
        if(vst[i] == 2) {
            son[fa[i]].pb(i);
        }
        if(! vst[i]) q.push(i);
    }
    F(i, pos, 2 * n - 1) {
        if(a[i]) break;
        int x = inf, y = fa[a[i - 1]], z = inf;
        // while(q.size() && (vst[q.top()] == 1 || vst[q.top()] == 3)) q.pop();
        if(q.size()) x = q.top();
        if(now[a[i - 1]] < son[a[i - 1]].size()) z = son[a[i - 1]][now[a[i - 1]]];
        // cout << i << " " << x << " " << y << " " << z << "\n";
        if((vst[a[i - 1]] == 2 || vst[a[i - 1]] == 3 || z < y) && z < x) {
            now[a[i - 1]] ++;
            a[i] = z;
            vst[a[i]] = 3;
            continue;
        }
        if(vst[a[i - 1]] == 2 || vst[a[i - 1]] == 3 || x < y) {
            a[i] = q.top();
            fa[a[i]] = a[i - 1];
            vst[a[i]] = 1;
            q.pop();
            continue;
        }
        vst[a[i - 1]] = 3;
        a[i] = fa[a[i - 1]];
    }
    F(i, 1, 2 * n - 1) cout << a[i] << " \n" [i == 2 * n - 1];
}
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t; cin >> t;
    while(t --) sol();
}
/*
1
5
1 0 0 0 3 4 3 2 1
*/

/*
1
5
1 5 0 0 0 0 2 3 1
*/
/*
9
5
1 2 3 2 0 2 1 5 1
5
1 2 3 0 0 2 1 5 1
5
1 2 0 0 0 2 1 5 1
5
1 2 0 0 0 0 1 5 1
5
1 0 0 0 0 0 1 5 1
5
1 0 0 0 0 0 0 5 1
5
1 0 0 0 0 0 0 0 1
5
1 0 0 0 0 0 0 0 0
5
0 0 0 0 0 0 0 0 0
*/