#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<string>
#include<ctime>
#include<map>
#include<set>
#include<bitset>
#include<queue>
#include<deque>
#include<vector>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
typedef long double ld;
inline int read(){
	int x=0;
	bool f=0;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-'){
			f=1;
		}
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		x=(x<<1)+(x<<3)+(ch^48);
		ch=getchar();
	}
	if(f){
		return -x;
	}
	return x;
}
inline uint readu(){
	uint x=0;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		x=(x<<1)+(x<<3)+(ch^48);
		ch=getchar();
	}
	return x;
}
void fp(){
	freopen(".in","r",stdin);
	freopen(".out","w",stdout);
}
int a[60],b[60];
int main(){
	//fp();
	int t=read();
	while(t--){
		int n=read(),i;
		for(i=1;i<=2*n;i++){
			a[i]=read();
		}
		sort(a+1,a+2*n+1);
		for(i=1;i<=n;i++){
			b[2*i]=a[i];
		}
		for(i=1;i<=n;i++){
			b[2*i-1]=a[i+n];
		}
		for(i=1;i<=2*n;i++){
			printf("%d ",b[i]);
		}
		puts("");
	}
	return 0;
}