answer.code: In function ‘int countIdealCompetitions(std::vector<std::__cxx11::basic_string<char> >&)’:
answer.code:9:5: error: ‘unordered_set’ was not declared in this scope
    9 |     unordered_set<string> uniqueSets;
      |     ^~~~~~~~~~~~~
answer.code:9:5: note: ‘std::unordered_set’ is only available from C++11 onwards
answer.code:9:25: error: expected primary-expression before ‘>’ token
    9 |     unordered_set<string> uniqueSets;
      |                         ^
answer.code:9:27: error: ‘uniqueSets’ was not declared in this scope
    9 |     unordered_set<string> uniqueSets;
      |                           ^~~~~~~~~~