#include <bits/stdc++.h>

using namespace std;

int main()
{
  int tn = 1;
  cin >> tn;
  while (tn--) {
    int n;
    cin >> n;
    vector<int> a_(n);
    for (auto &x : a_) cin >> x;
    
    int conclusion = 1e9+5;
    for (int k : array<int,2>{1, -1}) {
      vector<int> a(n);
      for (int i = 0; i < n; ++i) a[i] = k * a_[i];
    
      vector<array<int, 2>> pairs(n);
      for (int i = 0; i < n; ++i) pairs[i] = {a[i], i};
      sort(pairs.begin(), pairs.end());
      const int hi = pairs.back()[0];  // max
      const int lo = pairs.front()[0]; // min
      int ans = hi - lo; // max - min (pick x=0 case)
      
      vector<pair<int, vector<int>>> idx; // <x, {i : a[i]=x}> aka <x, indices>
      for (auto [x, i] : pairs) {
        if (idx.empty() || idx.back().first != x) idx.push_back({x, {}});
        idx.back().second.push_back(i);
      }
      
      // for (auto [x, ia] : idx) {
      //   cout << x << " [";
      //   for (auto i : ia) cout << i << " ";
      //   cout << "\n";
      // }
      
      // increase the min, make sure don't touch max
      
      vector<array<int, 3>> minPU; // <x, l, r> prefix union
      for (int i = 0; i < idx.size(); ++i) {
        const auto& [x, ia] = idx[i];
        int L = ia.front();
        int R = ia.back();
        if (i == 0) {
          minPU.push_back({x, L, R});
        } else {
          const auto& [y, ja] = idx[i-1];
          int L0 = ja.front();
          int R0 = ja.back();
          minPU.push_back({x, min(L, L0), max(R, R0)});
        }
      }
      
      int j = minPU.size()-1;
      for (int i = idx.size()-1; i >= 0; --i) {
        const auto& [x, ia] = idx[i];
        for (int k : ia) { // hit check
          while (j >= 0 && minPU[j][1] <= k && k <= minPU[j][2]) --j;
        }
        if (j >= 0) { // calculate
          int candidate = max(minPU[j][0] - lo, hi - x);
          ans = min(ans, candidate);
        } else break; // failed
      }
      conclusion = min(conclusion, ans);
    }
    
    cout << conclusion;
    cout << endl;
  }
}