CF814B An express train to reveries

 1 #include <iostream>
 2 using namespace std;
 3 
 4 const int N = 1005;
 5 
 6 int a[N], b[N], cnt[N], n, x, y;
 7 
 8 int main()
 9 {
10     cin >> n;
11     for (int i = 0; i < n; i++) cin >> a[i], cnt[a[i]]++;
12     for (int i = 0; i < n; i++) cin >> b[i];
13     for (int i = 1; i <= n; i++)
14     {
15         if (cnt[i] == 2) x = i;
16         else if (cnt[i] == 0) y = i;
17     }
18     for (int i = 0; i < n; i++)
19     {
20         if (a[i] == x)
21         {
22             a[i] = y;
23             int bad = 0;
24             for (int j = 0; j < n; j++)
25                 if (b[j] != a[j]) bad++;
26             if (bad == 1)
27             {
28                 for (int j = 0; j < n; j++) cout << a[j] << " ";
29                 return 0;
30             }
31             a[i] = x;
32         }
33     }
34     return 0;
35 }