#include "bits/stdc++.h"

using namespace std;

void solve() {
    int n;
    cin >> n;
    vector<int> arr(2 * n);
    for (auto &a : arr) cin >> a;
    sort(arr.begin(), arr.end());
    int i = 0, j = n;
    vector<int> res(2 * n);
    for (int k = 0; k < 2*n; k++) {
        if (k%2) {
            res[k] = arr[i++];
        } else {
            res[k] = arr[j++];
        }
    }
    for (auto &a : res) {
        cout << a << " ";
    }
    cout << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
}