Yandex Software Engineer Internship interview questions

It lasted for an hour. I got two easy problems, and the hard version of the second problem (which I didn't answer, but it didn't matter, because that was an extra question). The interviewer tried to correct my solutions, but 3 times did it wrong (one time the solution was just wrong, the second time he didn't know c++ syntax very well, the third time he didn't know how std::unordered_set has been written). After that interview, they wanted to find me a team.