【每日一题】打卡 42

原题链接：https://codeforces.com/problemset/problem/1593/D1

 

题面：

 思路：将所有的数减去最小的数，最后输出全部数的gcd即可。

#define _CRT_SECURE_NO_WARNINGS 1
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define FOR(a, b) for (int i = a; i <= b; i++)
#define ROF(a, b) for (int i = a; i >= b; i--)
#define FORj(a, b) for (int j = a; j <= b; j++)
#define ROFj(a, b) for (int j = a; j >= b; j--)
#define FORk(a, b) for (int k = a; k <= b; k++)
#define ROFk(a, b) for (int k = a; k >= b; k--)
#define mem(i, a) memset(i, a, sizeof(i))
#define ll long long
#define inf 0x3f3f3f3f
#define PII pair
#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1
#define int long long
#define endl '\n'
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define pi acos(-1.0)
using namespace std;
const int maxn = 2e6 + 5;
int a[maxn];
void solve() {
	int n, minn = inf;
	cin >> n;
	FOR(1, n) {
		cin >> a[i];
		minn = min(minn, a[i]);
	}
	sort(a + 1, a + n + 1);
	if (a[1] == a[n]) {
		cout << -1 << endl;
		return;
	}
	int sum = 0;
	FOR(1, n) {
		a[i] -= minn;
		sum = __gcd(sum, a[i]);
	}
	cout << sum << endl;
}
signed main() {
	cin.tie(0);
	cout.tie(0);
	ios::sync_with_stdio(0);
	int _;
	cin >> _;
	while (_--)
		solve();
	return 0;
}