#include <iostream>
#include<algorithm>
using namespace std;
int main() {
    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);
        for(int index =0;index<n;index++){
                cout<<a[index]<<" "<<a[n + index]<<" ";
        }
        cout<<endl;
    }
}