func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(0);     cout.tie(0);     cin.tie(0);     int t;     cin >> t;     while (t--) {       int n;       cin >> n;       string a, b;       cin >> a >> b;       vector<int> ans;       int l = 0, r = n - 1, x = 0;       for (int i = n - 1; i >= 0; --i) {         int cur = (a[r] -  0 ) ^ x;         if (cur == (b[i] -  0 )) {           if (l < r)             --r;           else             ++r;           continue;         }         cur = (a[l] -  0 ) ^ x;         if (cur == (b[i] -  0 )) {           ans.push_back(1);         }         ans.push_back(i + 1);         x ^= 1;         swap(l, r);         if (l < r)           --r;         else           ++r;       }       cout << ans.size() <<    ;       for (auto i : ans) cout << i <<    ;       cout <<   n ;     }   }   