#include <bits/stdc++.h>

#define int long long
#define x first
#define y second

using namespace std;

signed main() {
    cin.tie(0);
    cout.tie(0);
    ios_base::sync_with_stdio(0);

    int t;
    cin >> t;
    while(t--) {
        int n;
        cin >> n;
        vector<int> a(n);
        for(auto &i : a) {
            cin >> i;
        }
        int mx = a[0], mn = a[0], imx = 0, imn = 0;
        for(int i = 1; i < n; ++i) {
            if (a[i] > mx) {
                mx = a[i];
                imx = a[i];
            }
            if(a[i] < mn) {
                mn = a[i];
                imn = i;
            }
        }

        int l = 0, r = mx - mn;
        while(l < r) {
            int c = (l + r) / 2;

            bool f = false;
            {
                int tl = imx, tr = imx;
                while(tl - 1 >= 0 && a[tl - 1] >= mx - c) {
                    tl -= 1;
                }
                while(tr + 1 < n && a[tr + 1] >= mx - c) {
                    tr += 1;
                }

                bool ok = true;
                for (int i = 0; i < tl; ++i) {
                    if (a[i] > mn + c) {
                        ok = false;
                        break;
                    }
                }
                for (int i = tr + 1; i < n; ++i) {
                    if (a[i] > mn + c) {
                        ok = false;
                        break;
                    }
                }
                f = ok;
            }

            if(!f) {
                int tl = imn, tr = imn;
                while(tl - 1 >= 0 && a[tl - 1] <= mn + c) {
                    tl -= 1;
                }
                while(tr + 1 < n && a[tr + 1] <= mn + c) {
                    tr += 1;
                }

                bool ok = true;
                for (int i = 0; i < tl; ++i) {
                    if (a[i] < mx - c) {
                        ok = false;
                        break;
                    }
                }
                for (int i = tr + 1; i < n; ++i) {
                    if (a[i] < mx - c) {
                        ok = false;
                        break;
                    }
                }
                f = ok;
            }

            if(f) {
                r = c;
            } else {
                l = c + 1;
            }
        }

        cout << l << '\n';
    }
 
    return 0;
}