I was contacted by a recruiter.

We went back and forth for a while on my resume; I had to work on it seriously.

After submitting the resume, I heard nothing.

Eventually, I received an email notifying me of a phone interview.

I had to reschedule due to personal reasons.

I spent a week brushing up on basic computer science concepts.

In the interview, I struggled with some of the technical questions, but eventually arrived at what I thought were the right answers.

I submitted a code sample to the reviewer.

They suggested that my technical skills were not a match for the position they represented, and that I might be contacted by another reviewer.

So far, I have heard nothing.

Give the computational complexity of various algorithms to search a list of integers for a pair which add up to a given sum. Write a function to implement the fastest one.