#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
void solve(){
    int n;
    cin>>n;
    int arr[n*2];
    for (int i=0;i<2*n;i++){
        cin>>arr[i];
    }
    sort (arr,arr+n*2);
    bool flag = true;
    int l1 = 0;
    int l2 = n;
    for (int i=0;i<2*n;i++){
        if (flag){
            cout<<arr[l2]<<" ";
            l2++;
            flag = false;
        }
        else {
            cout<<arr[l1]<<" ";
            l1++;
            flag = true;
        }
    }
    cout<<endl;
    return;
}
int32_t main(){
IOS;
#ifndef ONLINE_JUDGE
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
    int t = 1;
    cin>>t;
    while (t--){
        solve();
    }
}
