import std.stdio;
import std.ascii;
import std.algorithm;
import core.stdc.stdio;

int main()
{
    int t = readInt!int;
    while (t--)
    {
        int n = readInt!int;
        auto a = new int[](2 * n);
        foreach(ref ai; a)
            ai = readInt!int;
        sort(a);
        debug writeln(a);
        auto low = a[0 .. n];
        auto high = a[n .. $];
        foreach(i; 0 .. n)
        {
            write(low[i], " ", high[i], " ");
        }
        writeln;
    }
    return 0;
}






/* INPUT ROUTINES */
int currChar;
static this()
{
    currChar = getchar();
}
char topChar()
{
    return cast(char) currChar;
}
void popChar()
{
    currChar = getchar();
}
auto readInt(T)()
{
    T num = 0;
    int sgn = 0;
    while (topChar.isWhite) popChar;
    while (topChar == '-' || topChar == '+') { sgn ^= (topChar == '-'); popChar; }
    while (topChar.isDigit) { num *= 10; num += (topChar - '0'); popChar; }
    if (sgn) return -num; return num;
}
string readString()
{
    string res = "";
    while (topChar.isWhite) popChar;
    while (!topChar.isWhite) { res ~= topChar; popChar; }
    return res;
}
