rt，WA test#4，错误信息:https://codeforces.com/problemset/submission/1902/237223869

代码：

# include <bits/stdc++.h>

# define ffor(i,name) \
	for (auto i = name.begin (); i != name.end (); i ++)

typedef long long ll;

using namespace std;

int t, n, a[100005], maxx, g, x;

ll sum;

map <int, int> vis;

int main () {

	ios::sync_with_stdio (0);

	cin.tie (0);

	cout.tie (0);

	cin >> t;

	while (t --) {

		sum = 0, maxx = -1e9, vis.clear ();

		cin >> n;

		for (int i = 0; i < n; ++ i) {

			cin >> a[i];

			vis[a[i]] = 1;

			maxx = max (maxx, a[i]);

		}

		if (n < 2) {

			cout << "1\n";

			continue ;

		}

		g = abs (a[1] - a[0]);

		for (int i = 2; i < n; ++ i)
			g = __gcd (g, abs (a[i] - a[i - 1]));

		for (int i = 0; i < n; ++ i)
			sum += (maxx - a[i]) / g;

		x = maxx;

		while (vis[x])
			x -= g, ++ sum;

		cout << sum << '\n';

	}

	return 0;

}