#include<iostream>
#include<cmath>
using namespace std;
int n,a[1145140],t,mix,mij,mx,mj;
bool check(int x){
	int l=1,r=n;
	for(int i=mij;i>=1;i--){
		if(a[i]+x>mx){
			l=i+1;
			break; 
		}
	}
	for(int i=mij;i<=n;i++){
		if(a[i]+x>mx){
		r=i-1;
		break;	
		}
	}
	//cout<<x<<" "<<r<<" "<<l<<endl;
	if(r<l)return 0;
	int minx=999999999;
	for(int i=1;i<=l-1;i++){
		minx=min(minx,a[i]);
	}
	for(int i=r+1;i<=n;i++){
		minx=min(minx,a[i]);
	}
	if(mix+x>minx)return 0;
	return 1;
}
bool c2(int x){
	int l=1,r=n;
	for(int i=mj;i>=1;i--){
		if(a[i]-x<mix){
			l=i+1;
			break; 
		}
	}
	for(int i=mj;i<=n;i++){
		if(a[i]-x<mix){
		r=i-1;	
		break;
		}
	}
		
		//cout<<x<<" "<<r<<" "<<l<<endl;
	if(r<l)return 0;
	int mjx=0;
	for(int i=1;i<=l-1;i++){
		mjx=max(mjx,a[i]);
	}
	for(int i=r+1;i<=n;i++){
		mjx=max(mjx,a[i]);
	}
	if(mx-x<mjx)return 0;
	return 1;
}
int main(){
	cin>>t;
	while(t--){
		cin>>n;
		if(n==1){
			int x;
			cin>>x;
			cout<<"0"<<endl;
		}
		mix=999999999,mx=-1,mij=0,mj=0;
		for(int i=1;i<=n;i++){
			scanf("%d",&a[i]);
			if(a[i]<mix){
				mix=a[i];
				mij=i;
			}
			if(a[i]>mx){
				mj=i;
				mx=a[i];
			}
		}
		//cout<<mj<<" vdf "<<mij<<endl;
		int l1=0,r1=mx-mix;
		while(l1<=r1){
			int mid=(l1+r1)>>1;
			if(check(mid))l1=mid+1;
			else{
				r1=mid-1;
			}
		}
		int l2=0,r2=mx-mix;
		while(l2<=r2){
			int mid=(l2+r2)>>1;
			if(c2(mid))l2=mid+1;
			else{
				r2=mid-1;
			}
		}
	//	cout<<r1<<" "<<r2<<" hj "<<endl;
		cout<<mx-mix-max(r1,r2)<<endl;
		for(int i=1;i<=n;i++)a[i]=0;
	}
}