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

#define F first
#define S second
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()

const int N = 2e5 + 200;
int n, a[N];

long long get() {
    int mx = *max_element(a + 1, a + n + 1);
    int mn = *min_element(a + 1, a + n + 1);
    long long ans = mx - mn;
    long long tl = 0, tr = ans;
    while (tl <= tr) {
        long long d = tl + tr >> 1;
        int lmn = n + 1, rmn = 0;
        for (int i = 1; i <= n; ++i) {
            if (a[i] < mx - d) {
                lmn = min(i, lmn);
                rmn = max(i, rmn);
            }
        }
        if (lmn > rmn) {
            ans = min(ans, d);
            tr = d - 1;
            continue;
        }
        int mx2 = -1e9;
        for (int i = lmn; i <= rmn; ++i) {
            mx2 = max(mx2, a[i]);
        }
        int x = mx - mx2;
        for (int i = lmn; i <= rmn; ++i) {
            a[i] += x;
        }
        long long kek = *max_element(a + 1, a + n + 1) - *min_element(a + 1, a + n + 1);
        if (kek <= d) {
            ans = min(ans, kek);
            tr = d - 1;
        }
        else {
            tl = d + 1;
        }
    }
    return ans;
}

void solve() {
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
    }
    long long ans = get();
    for (int i = 1; i <= n; ++i) {
        a[i] = (int)1e9 - a[i];
    }
    ans = min(ans, get());
    cout << ans << '\n';
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int T;
    cin >> T;
    while (T--) solve();

}