func_code_string: #include <bits/stdc++.h>   #pragma GCC optimize( Ofast )   #pragma GCC target( avx,avx2,fma )   using namespace std;   long long int mod = 1000000007;   long long int maxn = 200001;   long long int binpow(long long int a, long long int b, long long int mod) {     long long int res = 1;     while (b > 0) {       if (b % 2) {         res = (res * a) % mod;         b--;       }       a = (a * a) % mod;       b /= 2;     }     return res % mod;   }   long long int binpow(long long int a, long long int b) {     long long int res = 1;     while (b > 0) {       if (b % 2) {         res = (res * a);         b--;       }       a = (a * a);       b /= 2;     }     return res;   }   bool isPrime(long long int n) {     if (n == 1) return false;     for (long long int i = 2; i * i <= n; i++) {       if (n % i == 0) return false;     }     return true;   }   long long int mulmod(long long int a, long long int b) {     return ((a % mod) * (b % mod)) % mod;   }   long long int addmod(long long int a, long long int b) {     return (((a % mod) + (b % mod)) + mod) % mod;   }   void solve();   signed main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     ;     long long int t = 2;     cin >> t;     for (long long int tt = 1; tt <= t; tt++) {       solve();     }   }   void solve() {     long long int n;     cin >> n;     string s1, s2;     cin >> s1 >> s2;     vector<long long int> oper;     bool zero;     if (s1[0] ==  0 )       zero = true;     else       zero = false;     for (long long int i = 0; i < n - 1; i++) {       if (s1[i] != s1[i + 1]) {         oper.push_back(i + 1);         zero = !zero;       }     }     if (!zero) oper.push_back(n);     s1 = string(n,  0 );     zero = true;     for (long long int i = n - 1; i >= 0; i--) {       if (s2[i] ==  1  and zero == true) {         oper.push_back(i + 1);         zero = false;       }       if (s2[i] ==  0  and zero == false) {         oper.push_back(i + 1);         zero = true;       }     }     cout << oper.size() <<    ;     for (long long int i = 0; i < oper.size(); i++) cout << oper[i] <<    ;     cout <<   n ;   }   