iiitv/ChefLib

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// ~~~~~~~© Aashutosh Rathi~~~~~~
// ~~~~~~~~aashutosh001~~~~~~~~~~
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Result = Correct Answer (100 marks)

#include <bits/stdc++.h>
#include <stdio.h>

using namespace std;

#define mod(x)            x%1000000007;
#define MIN(n1, n2 )    ((n1) > (n2) ? (n2) : (n1))
#define MAX(n1, n2 )    ((n1) > (n2) ? (n1) : (n2))
#define MID(s, e)        (s+(e-s)/2)
#define FOR(i, a, b)    int i; for(i=(a);i<(b);i++)
#define FORD(i, a, b)    int i; for(i=(a);i>(b);i--)
#define show(a)            for(i=0;i<sizeof(a);i++) cout<<a[i]<<" ";
#define get(a)            for(i=0;i<sizeof(a);i++) cin>>a[i];
#define scanint(a)        scanf("%d",&a)
#define scanLLD(a)        scanf("%lld",&a)
#define scanstr(s)        scanf("%s",s)
#define scanline(l)     scanf(" %[^\n]",l);

typedef long int BIG;
typedef long long PAPA;

int main()
{
    std::ios_base::sync_with_stdio(false);
    int t;
    cin >> t;
    while(t--) {
        int n;
        cin >> n;
        int dn = 2*n;
        int a[dn], i;
        for (i = 0; i < dn; ++i) {
            cin >> a[i];
        }
        sort(a, a+dn);
        cout << a[n+n/2] << endl;
        for (i = 0; i < n; i++) {
            cout << a[i] << " " << a[n+i] <<" ";
        }
        cout << endl;
    }
    return 0;
}