Language: C++

#include <bits/stdc++.h>
using namespace std;
vvector<string> ans;
int n;

void dfs(int curr , int last , string s){
	if(curr == n){
		ans.push_back(s);
		return ;
	}
	if(s[curr] == '-'){
		s[curr] = 'a'+last;
		last += 1;
	}
	for(int i = curr+1 ; i < n ; i += 1){
		s[i] = s[curr];
	}
	dfs(curr+1,last,s);
}

int main(){
	cin >> n;
	string s = "";
	for(int i = 0 ; i < n ; i += 1){
		s += '-';
	}
	dfs(0,0,s);
	sort(ans.begin(),ans,end());
	for(string i : ans){
		cout << i << '\n';
	}
}

Compiler output:
a.cc:3:1: error: 'vvector' does not name a type
    3 | vvector<string> ans;
      | ^~~~~~~
a.cc: In function 'void dfs(int, int, std::string)':
a.cc:8:17: error: 'ans' was not declared in this scope; did you mean 'abs'?
    8 |                 ans.push_back(s);
      |                 ^~~
      |                 abs
a.cc: In function 'int main()':
a.cc:28:14: error: 'ans' was not declared in this scope; did you mean 'abs'?
   28 |         sort(ans.begin(),ans,end());
      |              ^~~
      |              abs
a.cc:28:33: error: no matching function for call to 'end()'
   28 |         sort(ans.begin(),ans,end());
      |                              ~~~^~
In file included from /usr/include/c++/14/bits/algorithmfwd.h:39,
                 from /usr/include/c++/14/bits/stl_algo.h:59,
                 from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/initializer_list:99:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/c++/14/string:53,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/range_access.h:74:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/range_access.h:85:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/range_access.h:106:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/valarray:1249:5: note: candidate: 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
 1249 |     end(valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1249:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/valarray:1265:5: note: candidate: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
 1265 |     end(const valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1265:5: note:   candidate expects 1 argument, 0 provided