The phone interview was brief and mechanical. The interviewer seemed clearly unprepared, inexperienced, and uninterested, as if it was an unwanted interruption to their day.

The interviewer had no knowledge of my previous conversations with the company or why exactly they were interviewing me. I was clearly passed their way expressly for the purpose of evaluating my technical ability. The interviewer asked two coding questions, using an online collaborative editor to view my progress. After the problem was sufficiently answered, the interviewer quickly ended the conversation.

As it has been described to me, Facebook has "streamlined" the hiring process in order to evaluate candidates very quickly. From my experience, this came off as unorganized and unprofessional.

My final impression was that the interviewer did not thoroughly evaluate me as a candidate but sufficed that I could answer two standard interview questions quickly and with explanation. Compared to other companies I interviewed with during the same period, this interview was not rigorous enough to really determine quality.

Given a telephone number, find all permutations of the letters, assuming 1=abc, 2=def, etc.