题解 | 元素方碑

#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

void solve() {
    int n; cin >> n;
    vector<i64> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    i64 sm = 0, sma = 0, smb = 0;
    for (int i = 0; i < n; i++) {
        sm += a[i];
        if (i & 1) sma += a[i];
        else smb += a[i];
    }
    i64 t = sm / n;
    cout << (sm % n == 0 && sma % t == 0 && smb % t == 0 && ((n & 1) ? smb == sma + t : smb == sma) ? "YES" : "NO") << '\n';
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int t = 1; cin >> t;
    while (t--) solve();
    return 0;
}