func_code_string: #include <bits/stdc++.h>   #define arr(i,n) for(ll i=0;i<n;i++)   #define ARR(i,n) for(ll i=n-1;i>=0;i--)   #define f(i,a,b)  for(ll i=a;i<b;i++)   #define F(i,a,b)  for(ll i=b-1;i>=a;i--)   #define float double   #define PI 3.14159265358979323846   #define pb push_back   #define mp make_pair   #define vi vector<ll>   #define ceil(a) (ll) ceil(a)   #define floor(a) (ll) floor(a)   #define pow(a,b) (ll) pow(a,b)   #define fixed(x) cout<<fixed<<setprecision(6)<<x;   #define vpii vector< pair<ll,ll> >   #define debug(x) cout<<(#x)<<  is  <<(x)<<endl   #define dbg(x,y)  cout<<#x<< =  <<x<<   and   <<#y<< = <<y<<endl   #define gcd(a,b) __gcd(a,b)   #define lcm(a,b) (a*(b/gcd(a,b)))   #define all(v) v.begin(),v.end()   #define array(a,n) arr(i,n) cout<<a[i]<<   ;   #define array2D(a,n,m) arr(i,n) {arr(j,m) cout<<a[i][j]<<   ; cout<<endl;}   #define IOS  ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)   typedef long long ll;   using namespace std;   const ll  mod = 1000000000 + 7;   void solve()   {       //code start here       ll n;       cin>>n;       n=2*n;       ll a[n];       arr(i,n) cin>>a[i];       sort(a,a+n);       ll start=0,end=n-1;       arr(i,n)       {           if(i%2==0) {cout<<a[start]; start++;}           else {cout<<a[end]; end--; }           cout<<   ;       }       cout<<endl;   }   int main()   {       IOS;       int t; cin>>t;       while(t--)  solve();       return 0;   }