CF1149A Prefix Sum Primes

思路：
质数一定是奇数。
实现：
 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int main()
 4 {
 5     int n, t, x, y;
 6     while (cin >> n)
 7     {
 8         x = y = 0;
 9         for (int i = 1; i <= n; i++)
10         {
11             cin >> t;
12             if (t & 1) x++;
13             else y++;
14         }
15         if (!y)
16         {
17             while (x) { cout << "1 "; x--; }
18             cout << endl;
19         }
20         else
21         {
22             cout << "2 "; y--;
23             if (x) { cout << "1 "; x--; }
24             while (y) { cout << "2 "; y--; }
25             while (x) { cout << "1 "; x--; }
26             cout << endl;
27         }
28     }
29     return 0;
30 }