func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 2e5 + 5;   const int inf = 0x3f3f3f3f;   const int mod = 1e9 + 7;   vector<int> ans;   char s1[maxn], s2[maxn];   int n;   void op(int x) {     for (int i = 1; i <= x; ++i) {       s1[i] = s1[i] ==  0  ?  1  :  0 ;     }     reverse(s1 + 1, s1 + 1 + x);     ans.push_back(x);   }   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     int t;     cin >> t;     while (t--) {       cin >> n;       cin >> s1 + 1 >> s2 + 1;       ans.clear();       for (int i = n; i >= 1; --i) {         if (s1[i] == s2[i]) continue;         if (i == 1)           op(1);         else {           if (s1[1] == s2[i]) op(1);           op(i);         }       }       cout << ((int)ans.size());       for (auto &v : ans) cout <<     << v;       cout <<   n ;     }     return 0;   }   