20分求调）

#include<bits/stdc++.h>
using namespace std;
#define ll long long
const ll N=2e5+2;
ll t;
ll n;
ll a[N];
int main(){
    cin>>t;
    while(t--){
        cin>>n;
        memset(a,0,sizeof(a));
        cin>>a[1];
        ll b=1;
        for(ll i=2;i<=n;i++){
            cin>>a[i];
            if(a[i]!=a[i-1]) b=0;
        }
        sort(a+1,a+n+1);
        
        if(b==1) cout<<"0\n";
        else cout<<max(a[1],a[n]-a[1])<<"\n";
    }

    return 0;
}