great_graphs.cpp

#include <bits/stdc++.h>
using namespace std;
//
#define ll long long
#define ull unsigned long long
#define mx 100010
#define mod 1000000007
#define inf INT_MAX
#define pi acos(-1)
#define endl '\n'
#define pb push_back
#define debug cout << "OK" << endl
#define fin freopen("input", "r", stdin)
#define Fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
//
int main() {
    ll t, n;
    cin >> t;

    while (t--) {
        ll n;
        cin >> n;

        vector<ll> vec(n);
        ll prv = 0, tot = 0;
        for (ll i = 0; i < n; i++) {
            cin >> vec[i];
            tot += vec[i];
        }
        sort(vec.begin(), vec.end());

        ll res = 0;
        for (ll i = 0; i < n - 1; i++) {
            prv += vec[i];
            res -= (tot - prv - (n - i - 1) * vec[i]);
        }

        cout << res + vec[n - 1] << endl;
    }
}