#include <bits/stdc++.h>
using namespace std;
const int N = 200010;
int a[N];
int main() {
  register int t;
  scanf("%d", &t);
  while (t--) {
    register int n;
    scanf("%d", &n);
    register int p = (n << 1);
    for (register int i = 1; i <= p; ++i) {
      scanf("%d", &a[i]);
    }
    sort(a + 1, a + p + 1);
    register int ans = 0x3f3f3f3f;
    for (register int i = 1; i <= n; ++i) {
      ans = min(ans, a[n + 1] - a[i]);
    }
    for (register int i = n + 1; i <= p; ++i) {
      ans = min(ans, a[i] - a[n]);
    }
    printf("%d\n", ans);
  }
  return 0;
}
