#include<bits/stdc++.h>
using namespace std;
const int N=1919810;
typedef long long ll;


ll a[N];
ll n;
int b[N];

ll mx,mn;


bool check1(ll mid){
    ll mx1=0;
    for(int i=1;i<=n;i++){
        if(a[i]<mid){
            b[i]=0;
            mx1=max(mx1,a[i]);
        }
        else b[i]=1;
    }
    //cout<<mx1<<endl;
    //for(int i=1;i<=n;i++) cout<<b[i]<<" ";
    //cout<<endl;
    ll need=mid-mn;
    if(mx1+need>mx){
        return false;
    }
    int j=1;
    int cnt0=0;
    for(int i=1;i<=n;i++){
        if(b[i]!=b[j]){
            if(b[j]==0) cnt0++;
            j=i;
        }
    }
    //cout<<cnt0<<endl;
    if(a[j]==0) cnt0++;
    return cnt0<=1;


}


ll gao1(){
    ll l=mn,r=mx;
    while(l<r){
        ll mid=l+r+1>>1;
        if(check1(mid)) l=mid;
        else r=mid-1;
    }
    //cout<<l<<endl;
    return mx-l;
}


bool check2(ll mid){
    ll mn1=1e18;
    for(int i=1;i<=n;i++){
        if(a[i]>mid) {
            b[i]=1;
            mn1=min(mn1,a[i]);
        }else b[i]=0;
    }

    ll need=mx-mid;
    if(mn1-need<mn) return false;


    int j=1;
    int cnt1=0;
    for(int i=1;i<=n;i++){
        if(b[i]!=b[j]){
            if(b[j]==1) cnt1++;
            j=i;
        }
    }
    if(b[j]==1) cnt1++;
    return cnt1<=1;

}


ll gao2(){
    ll l=mn,r=mx;
    while(l<r){
        ll mid=l+r>>1;
        if(check2(mid)) r=mid;
        else l=mid+1;
    }
    //cout<<l<<endl;
    return l-mn;
}

void __(){
    mn=1e18,mx=0;
    scanf("%lld",&n);
    for(int i=1;i<=n;i++) scanf("%lld",&a[i]);
    for(int i=1;i<=n;i++){
        mx=max(mx,a[i]);
        mn=min(mn,a[i]);
    }
    if(n==1) puts("0");
    else{
        ll ans=1e18;
        //check1(100);
        ans=min(ans,gao1());
        ans=min(ans,gao2());
        printf("%lld\n",ans);
    }
}

int main(){
    int _;
    cin>>_;
    while(_--){
        __();
    }
}