#include<bits/stdc++.h>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define ll long long
using namespace std;
void solve()
{
    int n,i,j,m,c=0;
    cin>>n;
    vector<int>v(2*n);
    for (int i = 0; i <2*n; ++i)
    {
    	cin>>v[i];
    }
    sort(v.begin(), v.end());
    i=0;
    while(i<n){
    	cout<<v[i]<<" "<<v[i+n]<<" ";
    	i++;
    }
	cout<<endl;
}

int main(){
ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	clock_t begin=clock();
	#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
	#endif // ONLINE_JUDGE
 	int t;
 	cin>>t;
 	while(t--)
 	solve();
	#ifndef ONLINE_JUDGE
 	clock_t end=clock();
 	cout<<"\n\nExecuted in : "<<((double)(end-begin)/CLOCKS_PER_SEC*1000)<<" ms"<<endl;	
 	#endif
	return 0;
}