#include <bits/stdc++.h>

using namespace std;

int main() {
  cin.tie(0)->sync_with_stdio(0);
  for (int tc = (cin >> tc, tc); tc--; ) {
    int n; cin >> n;
    vector<int> v(n); for (auto& x: v) cin >> x;
    multiset<int> si, so;
    for (int i = 0; i < n; ++i) so.insert(v[i]);
    int ans = 1e9;
    auto relax = [&] {
      int cans = 0;
      if (so.size()) cans = max(cans, *so.rbegin() - *so.begin());
      if (si.size()) cans = max(cans, *si.rbegin() - *si.begin());
      ans = min(ans, cans);
    };
    for (int i = 0, r = 0; r < n; ++i) {
      if (si.size()) {
        si.erase(si.find(v[i - 1]));
        so.insert(v[i - 1]);
      }
      relax();
      while (r < n) {
        so.erase(so.find(v[r]));
        si.insert(v[r]);
        relax();
        if (si.size() && (so.empty() || *so.rbegin() - *so.begin() < *si.rbegin() - *si.begin())) {
          si.erase(si.find(v[r]));
          so.insert(v[r]);
          break;
        } else ++r;
      }
    }
    cout << ans << '\n';
  }
}