func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e5 + 5;   int t;   int n;   string a, b;   int op[N];   int opb[N];   int bp = 0;   int ans = 0;   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cin >> t;     while (t--) {       cin >> n;       ans = 0;       cin >> a;       cin >> b;       if (a == b) {         cout << 0 << endl;         continue;       }       char st = a[0];       for (int i = 1; i < n; i++) {         if (a[i] != st) {           op[++ans] = i;           st = a[i];         }       }       if (a[n - 1] ==  0 ) op[++ans] = n;       st = b[0];       bp = 0;       for (int i = 1; i < n; i++) {         if (b[i] != st) {           opb[++bp] = i;           st = b[i];         }       }       if (b[n - 1] ==  0 ) opb[++bp] = n;       cout << ans + bp;       for (int i = 1; i <= ans; i++) cout <<     << op[i];       for (int i = bp; i >= 1; i--) cout <<     << opb[i];       cout << endl;     }     return 0;   }   