Eroare de compilare: user.cpp:7:1: error: ‘unordered_set’ does not name a type unordered_set<int> A; ^ user.cpp: In function ‘int main()’: user.cpp:21:13: error: ‘A’ was not declared in this scope A.insert(x); ^ user.cpp:26:13: error: ‘A’ was not declared in this scope A.erase(x); ^ user.cpp:29:18: error: ‘A’ was not declared in this scope fout << (A.find(x) != A.end()) << '\n'; ^