combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:16:51: error: no matching function for call to 'std::vector<std::__cxx11::basic_string<char> >::push_back(char&)'
16 | for( auto c : a ) if( s[0] != c ) bt.push_back( c );
| ~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/11/vector:67,
from /usr/include/c++/11/functional:62,
from /usr/include/c++/11/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/11/algorithm:74,
from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:65,
from combo.cpp:1:
/usr/include/c++/11/bits/stl_vector.h:1187:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::__cxx11::basic_string<char>; _Alloc = std::allocator<std::__cxx11::basic_string<char> >; std::vector<_Tp, _Alloc>::value_type = std::__cxx11::basic_string<char>]'
1187 | push_back(const value_type& __x)
| ^~~~~~~~~
/usr/include/c++/11/bits/stl_vector.h:1187:35: note: no known conversion for argument 1 from 'char' to 'const value_type&' {aka 'const std::__cxx11::basic_string<char>&'}
1187 | push_back(const value_type& __x)
| ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/11/bits/stl_vector.h:1203:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(std::vector<_Tp, _Alloc>::value_type&&) [with _Tp = std::__cxx11::basic_string<char>; _Alloc = std::allocator<std::__cxx11::basic_string<char> >; std::vector<_Tp, _Alloc>::value_type = std::__cxx11::basic_string<char>]'
1203 | push_back(value_type&& __x)
| ^~~~~~~~~
/usr/include/c++/11/bits/stl_vector.h:1203:30: note: no known conversion for argument 1 from 'char' to 'std::vector<std::__cxx11::basic_string<char> >::value_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
1203 | push_back(value_type&& __x)
| ~~~~~~~~~~~~~^~~