I attended the career fair and spoke to several engineers. Next week, they scheduled a phone screen interview via HackerRank. The interviewer asked several behavioral questions, such as:

• Give me a time when you received critical feedback.
• Give me a time when you had a difficult interaction with a customer.

After that, one simple data structures question was asked. I was asked to run the code and test all the scenarios. I was also asked about the time complexity.

You will be given n groups of integers. Find all of the common elements among all of the groups.