#include <bits/stdc++.h>
using namespace std;
/// MACROS
#define int long long
#define itn int
#define str string
#define sz size
#define ll long long
#define ull unsigned long long
#define ld long double
#define ii pair<int, int>
#define fs first
#define sc second
#define vi vector<int>
#define vii vector<ii>
#define pb push_back
#define pf push_front
#define fl '\n'
#define el endl
#define eps 1e-12
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
/// FUNCTIONS
#define db(x) cerr << #x << ": " << (x) << '\n';
#define lg2(x) __lg(x)
#define pi acos(-1)
#define YN(x) cout << ((x) ? ("YES") : ("NO")) << fl;
#define yn(x) cout << ((x) ? ("Yes") : ("No")) << fl;
#define precision(x) cout.setf(ios::fixed);cout.precision(x);

#define FL cout<<fl;
#define EL cout<<el;
#define ESP cout<<" ";

void print(int &x){cout<<x;}
void print(ii x){cout<<x.fs<<" "<<x.sc;}
void print(const auto &v){for(auto it: v){print(it);cout<<" ";}cout<<fl;}
void printp(const auto &v){for(auto it: v){print((ii)it);cout<<fl;}}
vi read(int cnt){vi v(cnt);for(int i=0;i<cnt;i++)cin>>v[i];return v;}
vii readp(int cnt){vii v(cnt);for(int i=0;i<cnt;i++)cin>>v[i].fs>>v[i].sc;return v;}
/////////////////////////////////////////////////////////////////////////////////////
template <typename T>
T s_prev(const std::set<T>& s, const T& val, const T& defaultValue) {
    auto it=s.lower_bound(val);
    if (it==s.begin()) return defaultValue;
    --it;
    return *it;
}
template <typename T>
T s_next(const std::set<T>& s, const T& val, const T& defaultValue) {
    auto it=s.upper_bound(val);
    if (it==s.end()) return defaultValue;
    return *it;
}
/////////////////////////////////////////////////////////////////////////////////////

itn n;
vi arr;

int spt[25][1000006];
void build(){
    for(int i=0;i<n;i++){spt[0][i]=arr[i];}
    for(int i=1;i<25;i++){
        for(int j=0;j+((int)1<<i)-1<n;j++){
            spt[i][j]=min(spt[i-1][j],spt[i-1][j+((int)1<<(i-1))]);
        }
    }
}
int qmin(int l,int r){
    if(l>r)return 1e12;
    int lg=lg2(r-l+1);
    return min(spt[lg][l],spt[lg][r-((int)1<<lg)+1]);
}

int spt2[25][1000006];
void build2(){
    for(int i=0;i<n;i++){spt2[0][i]=arr[i];}
    for(int i=1;i<25;i++){
        for(int j=0;j+((int)1<<i)-1<n;j++){
            spt2[i][j]=max(spt2[i-1][j],spt2[i-1][j+((int)1<<(i-1))]);
        }
    }
}
int qmax(int l,int r){
    if(l>r)return -1e12;
    int lg=lg2(r-l+1);
    return max(spt2[lg][l],spt2[lg][r-((int)1<<lg)+1]);
}

void solve(){
    cin>>n;
    arr=read(n);

    build();
    build2();

    int miv=1e12;
    for(int i=0;i<n;i++){
        miv=min(miv,arr[i]);
    }

    itn ans=1e12;

    for(int i=0;i<n;i++){
        int j=n-1;
        for(int mask=20;mask>=0;mask--){
            int nxt=j-((int)1<<mask);
            if(nxt>=i && qmax(nxt+1,n-1)<arr[i]){
                j=nxt;
            }
        }
        // cout<<i<<" "<<j<<fl;

        vi t;
        if(i==0 && j==n-1)continue;

        int mic=1e12;
        if(i){t.pb(qmin(0,i-1));mic=min(mic,qmin(0,i-1));}
        if(i)t.pb(qmax(0,i-1));
        if(j!=n-1){t.pb(qmin(j+1,n-1));mic=min(mic,qmin(j+1,n-1));}
        if(j!=n-1)t.pb(qmax(j+1,n-1));
        
        t.pb(mic + qmax(i,j)-qmin(i,j));

        sort(all(t));
        ans=min(ans,t.back()-t[0]);
    }
    
    for(int i=0;i<n;i++){
        int j=n-1;
        for(int mask=20;mask>=0;mask--){
            int nxt=j-((int)1<<mask);
            if(nxt>=i && qmin(nxt+1,n-1)>arr[i]){
                j=nxt;
            }
        }
        // cout<<i<<" "<<j<<fl;

        vi t;
        if(i==0 && j==n-1)continue;

        int mic=-1e12;
        if(i){t.pb(qmin(0,i-1));}
        if(i){t.pb(qmax(0,i-1));mic=max(mic,qmax(0,i-1));}
        if(j!=n-1){t.pb(qmin(j+1,n-1));}
        if(j!=n-1){t.pb(qmax(j+1,n-1));mic=max(mic,qmax(j+1,n-1));}
        
        t.pb(mic - (qmax(i,j)-qmin(i,j)) );

        sort(all(t));
        ans=min(ans,t.back()-t[0]);
    }

    cout<<ans<<fl;

}


int32_t main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int tc=1;
    cin>>tc;
    while(tc--){
        solve();
    }
    return 0;
}