CF814B An express train to reveries

思路：

模拟，枚举。

实现：

 #include <iostream>
 using namespace std;

 const int N = ;

 int a[N], b[N], cnt[N], n, x, y;

 int main()
 {
     cin >> n;
     for (int i = ; i < n; i++) cin >> a[i], cnt[a[i]]++;
     for (int i = ; i < n; i++) cin >> b[i];
     for (int i = ; i <= n; i++)
     {
         if (cnt[i] == ) x = i;
         else if (cnt[i] == ) y = i;
     }
     for (int i = ; i < n; i++)
     {
         if (a[i] == x)
         {
             a[i] = y;
             int bad = ;
             for (int j = ; j < n; j++)
                 if (b[j] != a[j]) bad++;
             if (bad == )
             {
                 for (int j = ; j < n; j++) cout << a[j] << " ";
                 return ;
             }
             a[i] = x;
         }
     }
     return ;
 }