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

#define fast ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
#define pb push_back

signed main()	{
	fast
	
	int t;
	cin >> t;
	while(t--)	{
		int n;
		cin >> n;

		int a[2*n];
		for(int i=0; i<2*n; i++)	{
			cin >> a[i];
		}

		sort(a, a+2*n);

		int b[2*n];
		for(int i=0; i<2*n; i++)	{
			if(i%2==0)	{
				b[i] = a[i/2];
			}
			else	b[i] = a[2*n-1-i/2];
		}

		for(int i=0; i<2*n; i++)	cout<<b[i]<<" ";
		cout<<endl;
	}	
}