#include<bits/stdc++.h>
using namespace std;
 
typedef long long int ll;
typedef long double ld;         
#define f(var,start,end) for(ll var = start; var <end ; ++var)
#define rf(var,start,end) for(ll var = start; var>=end ; var--)
#define pb push_back
#define mp make_pair
#define pf push_front
#define ff first
#define ss second
#define vll vector<ll>
#define pll pair<ll,ll> 
#define vpll vector<pll>
#define all(X) X.begin(),X.end()
#define nl cout<<"\n"
#define trace1(a) cerr << #a << ": " << a << endl;
#define trace2(a,b) cerr << #a << ": " << a << " " << #b << ": " << b << endl;
#define trace3(a,b,c) cerr << #a << ": " << a << " " << #b << ": " << b << " " << #c << ": " << c << endl;
#define trace4(a,b,c,d) cerr << #a << ": " << a << " " << #b << ": " << b << " " << #c << ": " << c << #d << ": " << d << endl;
#define OC freopen("input.txt" , "r", stdin); freopen("output.txt" , "w", stdout) 
#define MOD (ll)1e9+7; //change it for other mods
#define FAST_IO ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
 
int main()
{
	FAST_IO;
	ll t;
	cin>>t;
	while(t--)
	{
		ll n;
		cin>>n;
		vll vec;
		ll k;
		for(int i=0;i<2*n;i++)
		{
			cin>>k;
			vec.pb(k);
		}
		sort(all(vec));
		for(int i=0;i<n;i++)
		{
			cout<<vec[i]<<" ";
			cout<<vec[n+i]<<" ";
		}
		nl;
	}
}