A_Mean_Inequality.cpp

#include<bits/stdc++.h>
//Pain of discipline is better than pain of regret
#define pb push_back
#define mp make_pair 
#define fr first
#define sc second
#define clr(a) memset(a, 0, sizeof(a))
#define sz(x) x.size()
#define rep(n) for (ll i = 0; i < n; i++)
#define repc(i, n) for (ll i = 0; i < n; i++)
#define FOR(i, x, y) for (int i = x; i < y; i++)
#define DEC(i, x, y) for (int i = x; i >= y; i--)
#define all(v) v.begin(), v.end()
#define min3(a, b, c) min(a, min(b, c))
#define max3(a, b, c) max(a, max(b, c))
#define alla(a, n) a, a + n
 
using namespace std;
 
// Some typedef's
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;
 
// Some frequently used functions
template <typename T>
T modpow(T base, T exp, T modulus){  
    base %= modulus;  T result = 1;  
    while(exp > 0){    
        if(exp & 1) result = (result * base) % modulus;    
        base = (base * base) % modulus;    
        exp >>= 1;  
    }  
    return result;
}
ll lcm(ll a, ll b) { return (a * (b / __gcd(a, b))); }
 
// Some contants
const int inf = 1e9 + 7;
const double eps = 1e-6;
const double pi = 1.00 * acos(-1.00);

int main(){
	int t;
	cin >> t;
	while(t--){
        int n;
        cin >> n;
        ll a[2 * n];
        for(int i = 0; i < 2 * n;i++){
            cin >> a[i];
        }
        sort(a,a+2*n);
        for(int i = 0 ; i< n; i++){
            cout << a[i] << " " << a[i+n] << " ";
        }
        cout << endl;
	}
}