from sys import stdin
T = int(input())
for t in range(T):
n = int(stdin.readline().strip())
a = list(map(int, stdin.readline().strip().split()))
a.sort()
sofar = 0
for i in range(n):
l_next, r_next = 0, 0
if i > 0:
l_next = a[i] - a[i-1]
if i < n-1:
r_next = a[i+1] - a[i]
left = a[i] - a[0]
right = a[n-1] - a[i]
sofar = max(sofar, max(l_next, r_next) + max (left, right))
print(sofar)
#include<bits/stdc++.h>
using namespace std;
void solve()
{
int n;
cin >> n;
vector<int> a(n);
for (int i = 0; i < n; i++)
cin >> a[i];
sort(a.begin(), a.end());
int ans = 0;
for (int i = 0; i < n-2; i++)
ans = max(ans, a[n - 1] - a[i] + a[i+1] - a[i]);
for (int i = n - 1; i > 0; i--)
ans = max(ans, a[i] - a[i - 1] + a[i] - a[0]);
//
cout << ans << endl;
}
int main()
{
int t;
cin >> t;
while (t--)
solve();
return 0;
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