#include <bits/stdc++.h>
using namespace std;
using ll = long long;

void solve() {
  int n; cin >> n;
  vector<ll> a(n);
  for(int i = 0; i < n; i++) cin >> a[i];
  ll ok = 2000000100LL, ng = -1;
  while(ok - ng > 1) {
    ll mid = midpoint(ok, ng);
    bool valid = false;
    int l = n;
    multiset<ll> in, out;
    for(int i = 0; i < n; i++) out.insert(a[i]);
    for(int r = n; r >= 0; r--) {
      auto expandable = [&](int nl) {
        if(nl < 0) return false;
        if(in.empty()) return true;
        ll mx = max(*in.rbegin(), a[nl]);
        ll mn = min(*in.begin(), a[nl]);
        if(mx-mn <= mid) return true;
        return false;
      };
      while(l>0 && expandable(l-1)) {
        l--;
        out.erase(out.find(a[l]));
        in.insert(a[l]);
      }
      //cerr << mid << ' ' << l << ' ' << r << endl;
      //cerr << '#' << ssize(out) << endl;
      //if(!out.empty()) cerr << ' ' << *out.rbegin() << ' ' << *out.begin() << endl;
      if(out.empty() || (*out.rbegin()-*out.begin() <= mid)) {
        valid = true;
        break;
      }
      if(r==0) break;
      assert(!in.empty());
      in.erase(in.find(a[r-1]));
      out.insert(a[r-1]);
    }
    if(valid) ok = mid;
    else ng = mid;
  }
  cout << ok << '\n';
}

int main() {
  int t; cin >> t;
  while(t--) solve();
}