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

int main() {
	int t,n,i,j;
	cin>>t;
	while(t--){
	    cin>>n;
	    n = n*2;
	    vector<int> arr(n),ans(n,0);
	    for(i=0;i<n;i++)
	        cin>>arr[i];
	    
	    sort(arr.begin(),arr.end());
	    
	    i=0;
	    j=0;
	    while(j<n){
	        ans[j] = arr[i];
	        i++;
	        j+=2;
	    }
	    j = 1;
	    while(j<n){
	        ans[j]=arr[i];
	        i++;
	        j+=2;
	    }
	    
	    for(i=0;i<n;i++)
	        cout<<ans[i]<<" ";
	    cout<<endl;
	}
	
	return 0;
}
