CF1149A Prefix Sum Primes

思路：

质数一定是奇数。
实现：

 #include <bits/stdc++.h>
 using namespace std;
 int main()
 {
     int n, t, x, y;
     while (cin >> n)
     {
         x = y = ;
         for (int i = ; i <= n; i++)
         {
             cin >> t;
             if (t & ) x++;
             else y++;
         }
         if (!y)
         {
             while (x) { cout << "1 "; x--; }
             cout << endl;
         }
         else
         {
             cout << "2 "; y--;
             if (x) { cout << "1 "; x--; }
             while (y) { cout << "2 "; y--; }
             while (x) { cout << "1 "; x--; }
             cout << endl;
         }
     }
     return ;
 }