#include <bits/stdc++.h>
using namespace std;
#define ll long long int
void solve();
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("error.txt", "w", stderr);
	freopen("output.txt", "w", stdout);
#endif

	ll t = 1;
	/*is Single Test case?*/ cin >> t;
	while (t--) {
		solve();
		cout << "\n";
	}

	cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
	return 0;
}
void solve()
{
	ll n;
	cin>>n;
	vector<ll>a(2*n);
	for(auto &it:a)
		cin>>it;
	sort(a.begin(),a.end());
	for(ll i=0;i<n;i++)
		cout<<a[i]<<" "<<a[i+n]<<" ";
}