#include <bits/stdc++.h>
#define ll long long
#define int long long
#define ff first
#define ss second
#define PI pair<int, int>
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define bust ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
const int INF = (int)1e9 + 7;

void solve(){
    int n;
    cin  >> n;
    ll a[n];
    ll mx = 0, mxi = 0, mn = INF, mni = 0;
    for(int i = 0; i < n; ++i){
        cin >> a[i];
        if(a[i] > mx){
            mx = a[i];
            mxi = i;
        }
        if(a[i] < mn){
            mn = a[i];
            mni = i;
        }
    }

    ll l = -1, r = mx+1000;
    while(l < r - 1){
        ll mid = (l + r)/2;
        vector<bool> used(n, false);
        int li = mni;
        while(li >= 0 && a[li] <= mn + mid){
            used[li] = 1;
            ++li;
        }
        int ri = mni;
        while(ri < n && a[ri] <= mn + mid){
            used[ri] = 1;
            ++ri;
        }

        bool f = 0;
        ll mx2 = 0, mn2 = INF;
        for(int i = 0; i < n; ++i){
            if(used[i]) continue;
            mx2 = max(mx2, a[i]);
            mn2 = min(mn2, a[i]);
        }

        if(mx2-mn2 > mid){
            l = mid;
        }
        else{
            r = mid;
        }
//        cout << l << " " << r << '\n';
    }
//    cout << r << '\n';

    ll l2 = -1, r2 = mx+1000;
    while(l2 < r2 - 1){
        ll mid = (l2 + r2)/2;
        vector<bool> used(n, false);
        int li = mxi;
        while(li >= 0 && a[li] >= mx - mid){
            used[li] = 1;
            --li;
        }
        int ri = mxi;
        while(ri < n && a[ri] >= mx - mid){
            used[ri] = 1;
            ++ri;
        }

        bool f = 0;
        ll mx2 = 0, mn2 = INF;
        for(int i = 0; i < n; ++i){
            if(used[i]) continue;
            mx2 = max(mx2, a[i]);
            mn2 = min(mn2, a[i]);
        }

        if(mx2-mn2 > mid){
            l2 = mid;
        }
        else{
            r2 = mid;
        }
//        cout << l2 << " " << r2 << '\n';
    }
//    cout << r2 << '\n';
    ll ans = min(r, r2);
    cout << ans << '\n';
}

signed main() {
    bust
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}