#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define ov4(a, b, c, d, name, ...) name
#define rep3(i, a, b, c) for(ll i = (a); i < (b); i += (c))
#define rep2(i, a, b) rep3(i, a, b, 1)
#define rep1(i, n) rep2(i, 0, n)
#define rep0(n) rep1(aaaaa, n)
#define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define per(i, a, b) for(ll i = (a)-1; i >= (b); i--)
#define fore(e, v) for(auto&& e : v)
#define all(a) begin(a), end(a)
#define sz(a) (int)(size(a))
#define lb(v, x) (lower_bound(all(v), x) - begin(v))
#define eb emplace_back

template<typename T, typename S> bool chmin(T& a, const S& b) { return a > b ? a = b, 1 : 0; }
template<typename T, typename S> bool chmax(T& a, const S& b) { return a < b ? a = b, 1 : 0; }

const int INF = 1e9 + 100;
const ll INFL = 3e18 + 100;

#define i128 __int128_t

struct _ {
   _() { cin.tie(0)->sync_with_stdio(0), cout.tie(0); }
} __;


const int m = 20;
void solve() {
    int n;cin >> n;
    vl a(n);rep(i, n) cin >> a[i];

    ll l = *min_element(all(a)), r = *max_element(all(a));

    auto check = [&](ll M) -> bool {
        if (r - l <= M) return true;
        ll d = r - l - M;
        int L = 1e9, R = -1;
        rep(i, n) {
            if (a[i] > l + M) {
                L = min(L, (int)i);
                R = max(R, (int)i);
            }
        }
        bool FLAG = 1;
        rep(i, L, R) {
            if (a[i] - d < l) FLAG = 0;
        }
        if (FLAG) return true;
        L = 1e9, R = -1;
        rep(i, n) {
            if (a[i] < r - M) {
                L = min(L, (int)i);
                R = max(R, (int)i);
            }
        }
        FLAG = 1;
        rep(i, L, R) {
            if (a[i] + d > r) FLAG = 0;
        }
        if (FLAG) return true;
        return false;
    };

    ll ok = 1e9 + 10, ng = -1;
    while (ok - ng > 1) {
        ll mid = (ok + ng) / 2;
        if (check(mid)) ok = mid;
        else ng = mid;
    }
    cout << ok << endl;
}   

int main() {
    int T;cin >> T;
    // int T = 1;
    while (T--) {
        solve();
    }
}