/in/foo.cc: In function 'void meet_in_the_middle(const std::vector<int>&, std::vector<std::__cxx11::basic_string<char> >*, state)':
/in/foo.cc:99:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < initial_letters.size(); i++) {
                    ~~^~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc: In lambda function:
/in/foo.cc:114:22: error: expected unqualified-id before '[' token
             for(auto [now, cnt]: mp)
                      ^
/in/foo.cc:114:22: error: expected ';' before '[' token
/in/foo.cc:114:23: error: 'now' was not declared in this scope
             for(auto [now, cnt]: mp)
                       ^~~
/in/foo.cc:114:28: error: 'cnt' was not declared in this scope
             for(auto [now, cnt]: mp)
                            ^~~
/in/foo.cc: In lambda function:
/in/foo.cc:114:32: error: expected '{' before ':' token
             for(auto [now, cnt]: mp)
                                ^
/in/foo.cc: In lambda function:
/in/foo.cc:114:32: error: expected ';' before ':' token
/in/foo.cc:114:32: error: expected primary-expression before ':' token
/in/foo.cc:114:32: error: expected ')' before ':' token
/in/foo.cc:114:32: error: expected primary-expression before ':' token
/in/foo.cc:112:17: warning: unused variable 'c' [-Wunused-variable]
         for(int c : initial_letters_half) {
                 ^
/in/foo.cc: In function 'void meet_in_the_middle(const std::vector<int>&, std::vector<std::__cxx11::basic_string<char> >*, state)':
/in/foo.cc:177:33: warning: unused variable 'cnt' [-Wunused-variable]
      auto state = _.first; auto cnt = _.second; 
                                 ^~~