#include "bits/stdc++.h"

#define ff first
#define ss second
#define pb push_back
#define ll long long
#define db puts("*****")
#define sz(x) int(x.size())
#define pii pair <int , int>
#define mid(x , y) ((x+y)>>1)
#define all(x)	x.begin(),x.end()
#define y1 your_name_engraved_herein

using namespace std;

const int N = 2e5+2;
const int K = 1e3+2;
const int MOD = 1e9+7;

template<class T> bool umin(T& a, T b) { if(a > b){ a = b; return 1; } return 0; }
template<class T> bool umax(T& a, T b) { if(a < b){ a = b; return 1; } return 0; }

void solve(){
    int n; scanf("%d", &n);
    int lmin = 0, rmin = 0, mini = MOD;
    int lmax = 0, rmax = 0, maxi = 0;
    vector<int> a(n);
    for(int i=0; i<n; i++){
        scanf("%d", &a[i]);
        mini = min(mini, a[i]);
        maxi = max(maxi, a[i]);
    }
    for(int i=0; i<n; i++){
        if(a[i] == mini){
            if(!lmin) lmin = i;
            rmin = i;
        }
        if(a[i] == maxi){
            if(!lmax) lmax = i;
            rmax = i;
        }
    }
    
    int med = mid(maxi, mini);
    int ln = lmin, rn = rmin;
    while(ln > 0 && a[ln-1] <= med) ln--;
    while(rn < n-1 && a[rn+1] <= med) rn++;
    int lx = lmax, rx = rmax;
    while(lx > 0 && a[lx-1] > med) lx--;
    while(rx < n-1 && a[rx+1] > med) rx++;
    int ans = 0;
    auto getans = [&](int x, int y){
        int minInside = *min_element(a.begin() + x, a.begin() + y + 1);
        int maxInside = *max_element(a.begin() + x, a.begin() + y + 1);
        int minOutside = MOD, maxOutside = 0;
        for(int i=0; i<x; i++){
            umin(minOutside, a[i]);
            umax(maxOutside, a[i]);
        }
        for(int i=y+1; i<n; i++){
            umin(minOutside, a[i]);
            umax(maxOutside, a[i]);
        }
        int diff1 = maxInside - minInside;
        int diff2 = maxOutside - minOutside;
        if(diff2 == MOD) diff2 = 0;
        return max(diff1, diff2);
    };
    if(lmin < lmax && rmax < rmin){
        ans = getans(lx, rx);
    } else if(lmax < lmin && rmin < rmax){
        ans = getans(ln, rn);
    } else if(min(rmin, rmax) > max(lmin, lmax)){
        ans = (maxi - mini);
    } else {
        ans = min(getans(ln, rn), getans(lx, rx));
    }
    printf("%d\n", ans);
}

int main(){
    int testcase = 1;
    scanf("%d", &testcase);
    while(testcase--){
        solve();
    }
    return 0;
}