#include "bits/stdc++.h"
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int tt;
  cin >> tt;
  while(tt--) {
    int n;
    cin >> n;
    vi a(n);
    for (auto& x : a) cin >> x;
    int mn = *min_element(all(a));
    int mx = *max_element(all(a));
    int ans = mx - mn;
    {
      auto check = [&](int k)->bool {
        vi b(n);
        int inc = k - mn;
        rep(i, 0, n) {
          if (a[i] < k) {
            b[i] = 1;
            if (a[i] + inc > mx) return false;
          }
        }
        int segs = 0;
        bool on = false;
        rep(i, 0, n) {
          if (b[i] == 1) {
            if (!on) {
              segs++;
            }
            on = true;
          } else {
            on = false;
          }
        }
        return segs <= 1;
      };

      int l = mn, r = mx;
      while(l < r) {
        int m = (l+r+1)/2;
        if (check(m)) {
          l = m;
        } else {
          r = m-1;
        }
      }
      ans = min(ans, mx - l);
    }
    {
      auto check = [&](int k)->bool {
        vi b(n);
        int dec = mx - k;
        rep(i, 0, n) {
          if (a[i] > k) {
            b[i] = 1;
            if (a[i] - dec < mn) return false;
          }
        }
        int segs = 0;
        bool on = false;
        rep(i, 0, n) {
          if (b[i] == 1) {
            if (!on) {
              segs++;
            }
            on = true;
          } else {
            on = false;
          }
        }
        return segs <= 1;
      };

      int l = mn, r = mx;
      while(l < r) {
        int m = (l+ r)/2;
        if (check(m)) {
          r = m;
        } else {
          l = m+1;
        }
      }
      ans = min(ans, l - mn);
    }
    cout << ans << '\n';
  }
}