B_Black_Cells.cpp

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector<bool> vbl;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<string> vstr;
typedef vector<pll> vpll;

#define endl '\n'
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
constexpr ll mod = 1000000007;

inline void Parvez() { ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0); }
template<class T>inline istream& operator>>(istream& in, vector<T>& v) { for (T& x : v) { in >> x; }return in; }template<class T>inline ostream& operator<<(ostream& out, vector<T>& v) { for (ll i = 0;i < v.size() - 1;i++) { out << v[i] << ' '; }out << v[v.size() - 1];return out; }
inline void input() {}template<class H, class... T>inline void input(H&& h, T &&...t) { cin >> h;input(forward<T>(t)...); }inline void print() { cout << endl; }template<class H, class... T>inline void print(H&& h, T &&...t) { cout << h;if (sizeof...(t) != 0)cout << ' ';print(forward<T>(t)...); }




void solution(ll& T) {
	ll n; cin >> n; vector<ll> a(n); cin >> a;
	ll ans = 1e18;

	auto upd = [&](vector<ll> a) {
		sort(a.begin(), a.end());
		ll res = 0;
		for (ll i = 0; i < (ll)a.size(); i += 2) {
			res = max(res, a[i + 1] - a[i]);
		}
		ans = min(ans, res);
		};

	if (n % 2 == 0) {
		upd(a);
		print(ans);
		return;
	}

	for (ll i = 0; i < n; ++i) {
		for (ll x : {-1, 1}) {
			a.push_back(a[i] + x);
			upd(a);
			a.pop_back();
		}
	}

	print(ans);
}

signed main() {
	Parvez();
	ll TT = 1;
	cin >> TT;
	for (ll T = 1;T <= TT;T++)
		solution(T);
	return 0;
}