1 #include<stdio.h>
 2 
 3 char s[100005];
 4 char s1[100005];
 5 char s3[100005];
 6 int st[500005], tp;
 7 
 8 int main()
 9 {
10     int t;
11     scanf("%d",&t);
12     while(t--)
13     {
14         int n;
15         scanf("%d",&n);
16         scanf("%s",s);
17         scanf("%s",s1);
18         for
 
(int i = 0; i < n; i++) s[i] -= '0',s1[i] -= '0';
19         s[n] = s1[n] = s3[n] = 0;
20         int cnt = 0;
21         do
22         {
23             tp = 0;
24             st[++tp] = n-cnt;
25             for(int i = 0; i < n; i++) s3[i] = ((i<n-cnt)?(s[i]^1):s[i]);
26             for(int i = 0; i < (n-cnt)/2
 
; i++) s3[i] ^= s3[n-cnt-i-1] ^= s3[i] ^= s3[n-cnt-i-1];
27             for(int i = 0; i < n; i++)
28             {
29                 if(s3[i]^s1[i])
30                 {
31                     int j = i+1;
32                     while(s3[j]^s1[j] && s3[j] == s3[i]) j++;
33                     st[++tp] = j;
 
34                     if(!i) {i=j-1;continue;}
35                     st[++tp] = j-i;
36                     st[++tp] = j;
37                     i = j-1;
38                 }
39             }
40             cnt = (cnt * cnt + cnt+1) % n;
41         }while(tp > 2*n);
42         printf("%d",tp);
43         for(int i = 1; i <= tp; i++) printf(" %d%s",st[i],i==tp?"\n":"");
44         if(!tp) puts("");
45     }
46     return 0;
47 }