I understand, I need to write quick sort alogorithm but it was not in my brain. Just go for bubble sort and I request him, can I do it in C++ because I never solve contest programming problems in swift. He gave me the chance. And I solved the problem but it was O(n2) and I knew that, I may not get the job. But surprised the overall inveriew process. A bit sad and I feel unlucky. Can't forget his ha ha ha after hearing my name and surprised someone can call loudly someone's name is funny. It destroied my confidence.... Hopefully next time I may get a nice interviewer.