题解 | 元素方碑

#include <iostream>
#include <vector>
#define int long long
using namespace std;

signed main() {
    int t;cin>>t;
    while(t--){
        int n;cin>>n;
        vector<int> a(n);
        int odd = 0, even = 0;
        int co = 0, ce = 0;
        for(int i = 0;i < n;++i){
            cin>>a[i];
            if(i & 1){
                odd+=a[i];
                co++;
            }else even+=a[i],ce++;
        }
        if(co==0 || ce== 0){
            cout<<"YES\n";
            continue;
        }

        if(odd/co == even / ce && (odd + even) % n == 0){
            cout<<"YES\n";
            continue;
        }
        cout<<"NO\n";
    }
}
// 64 位输出请用 printf("%lld")