#include<bits/stdc++.h>
using namespace std;

typedef long long ll;

const int N = 3e5 + 10;
bool app[N];
int a[2 * N], par[N];

deque<int> get_path(int arr[], int n) {
    int last = 0;
    for (int i = 1; i <= n && a[i]; ++i) {
        if (!par[a[i]] && a[i] != a[1]) par[a[i]] = a[i - 1];
        last = a[i];
    }
    deque<int> ret; 
    while (last) {
        ret.push_front(last);
        last = par[last];
    }
    return ret;
}

void construct(int &p, int root, set<int> values) {
    if (!values.size()) return;
    if (*values.begin() < root) {
        for (set<int>::iterator it = values.begin(); it != values.end(); ++it) {
            a[p++] = *it;
            if (it != values.begin()) a[p++] = *values.begin();
        }
        a[p++] = root;
    }
    else {
        for (int i : values) {
            a[p++] = i;
            a[p++] = root;
        }
    }
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    if (fopen("qoj_5665.inp", "r")) {
        freopen("qoj_5665.inp", "r", stdin);
        freopen("qoj_5665.out", "w", stdout);
    }

    #ifdef LOCAL_MACHINE 
        if (fopen("task.inp", "r")) {
            freopen("task.inp", "r", stdin);
            freopen("task.out", "w", stdout);
        }
    #endif

    int nTest; cin >> nTest;
    while(nTest--) {
        int n; cin >> n; n = 2 * n - 1;
        for (int i = 1; i <= n; ++i) cin >> a[i];
        
        if (n == 1) {
            cout << "1\n";
            continue;
        }

        if (!a[1] && !a[n]) a[1] = a[n] = 1;
        else a[1] = a[n] = max(a[1], a[n]);

        deque<int> fx = get_path(a, n);
        reverse(a + 1, a + n + 1);
        deque<int> fy = get_path(a, n);
        reverse(a + 1, a + n + 1);

        while (fx.size() > 1 && fy.size() > 1 && fx[1] == fy[1]) {
            fx.pop_front();
            fy.pop_front();
        }
        fy.pop_front();

        reverse(fx.begin(), fx.end()); 
        for (int i : fy) fx.push_back(i);

        set<int> out;
        for (int i = 1; i <= n; ++i) app[a[i]] = 1;
        for (int i = 1; i <= n / 2 + 1; ++i) if (!app[i]) out.insert(i);

        int L = 1;
        while (a[L] && L <= n) ++L;

        for (int i = 0; i + 1 < (int) fx.size(); ++i) {
            int cur = fx[i], nxt = fx[i + 1];

            set<int> proc;
            for (int x : out) {
                if (x < nxt) proc.insert(x);
                else break;
            }
            for (int i : proc) out.erase(i);

            if (proc.size()) construct(L, cur, proc);

            a[L++] = nxt;
        }

        construct(L, fx.back(), out);

        for (int i = 1; i <= n; ++i) cout << a[i] << " "; 
        cout << "\n";

        for (int i = 1; i <= n / 2 + 1; ++i) app[i] = par[i] = 0;
    }
}

// ඞඞඞඞඞ you sus