#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef long long ll;
const int N=1e6+7;
int a[N],ans;
int px[N],sx[N];
int pn[N],sn[N];
int n;
void wk(){int l,r;
    sx[n+1]=-2e9,sn[n+1]=2e9;
    px[0]=-2e9,pn[0]=2e9;
    for(int i=1;i<=n;i++)px[i]=max(px[i-1],a[i]),pn[i]=min(pn[i-1],a[i]);
    for(int i=n;i;i--)sx[i]=max(sx[i+1],a[i]),sn[i]=min(sn[i+1],a[i]);
    vector<int>id(n);
    std::iota(id.begin(), id.end(), 1);
    std::sort(id.begin(), id.end(),[&](int x,int y){
        return a[x]>a[y];
    });
    l=r=id[0];
    int mx=a[l],mn=a[r];
    for(auto i:id){
        int nl=min(l,i),nr=max(r,i);
        while(l>nl){
            l--;
            mx=max(mx,a[l]);
            mn=min(mn,a[l]);
        }
        while(r<nr){
            r++;
            mx=max(mx,a[r]);
            mn=min(mn,a[r]);
        }
        ans=min(ans,max(mx-mn,max(px[l-1],sx[r+1])-min(pn[l-1],sn[r+1]) ) );
    }
}

void solve(){
    ans=2e9;
    cin>>n;
    int mx=0;
    for(int i=1;i<=n;i++)cin>>a[i];
    wk();
    for(int i=1;i<=n;i++)a[i]=-a[i];
    wk();
    cout<<ans<<'\n';
}

signed main(){
    ios::sync_with_stdio(false);
    int T=1;
    cin>>T;
    while(T--)solve();
}