#include<bits/stdc++.h>
using namespace std;
const int inf = 1e9 + 7;
const int N = 200022;
int a[N];
void solve() {
    int n;
    scanf("%d", &n);
    for(int i = 0; i < n; i++) {
        scanf("%d", &a[i]);
    }
    int mx = *max_element(a, a + n);
    int mn = *min_element(a, a + n);
    int le = 0, ri = inf;
    while(le != ri) {
        int mid = (le + ri) / 2;
        bool ok = false;
        for(int d = 0; d < 2; d++) {
            int st = n, ed = -1, cnt = 0;
            bool flag = true;
            for(int i = 0; i < n; i++) {
                if(a[i] < mx - mid) {
                    st = min(st, i);
                    ed = max(ed, i);
                    cnt++;
                    if(a[i] + (mx - mid - mn) > mx) {
                        flag = false;
                    }
                }
            }
            if(flag) {
                ok |= cnt == 0 || (ed - st + 1) == cnt;
            }

            for(int i = 0; i < n; i++) {
                a[i] = -a[i];
            }
            swap(mn, mx);
            mx = -mx;
            mn = -mn;
        }
        if(ok) {
            ri = mid;
        } else {
            le = mid + 1;
        }
    }
    printf("%d\n", le);
}
int main() {
    int t;
    scanf("%d", &t);
    for(int qq = 1; qq <= t; qq++) {
        solve();
    }
}