题解 | 元素方碑

// 这题的主要难度在于处理输入
#include <cstddef>
#include <iostream>
using namespace std;
#include <cstdlib>
#include <vector>
#include <sstream>

int main() {
    int t, n;
    string s;
    cin >> t;
    while (t--) { // 注意 while 处理多个 case
        vector<int> v;
        v.clear();
        cin >> n;
        cin.ignore();
        getline(cin, s);
        istringstream ss(s);
        int sum = 0;
        while(getline(ss, s, ' ')){
            v.push_back(stoi(s));
            sum += stoi(s);
        }
        if(sum % n != 0){
            cout << "NO" << endl;
            continue;
        }
        sum /= n;
        for(int i = 0; i < n - 2; i++){
            v[i + 2] -= sum - v[i];
            v[i] = sum;
        }
        bool b = true;
        for(auto p:v){
            // cout << p << " " <<sum << endl;
            if(p != sum){
                cout << "NO" << endl;
                b =false;
                break;
            }
        }
        if(b){
            cout << "YES" << endl;
        }
    }
}
// 64 位输出请用 printf("%lld")