I reached out to a hiring manager on LinkedIn and stated I was interested in Uber's engineering department. She connected me with a recruiter, who emailed me to schedule a one-hour technical phone interview.

I received a confirmation email with a Codepair link to use during the interview, and a link to Uber's careers site for an idea of what it's like to work for Uber.

My interviewer called me on time. While he wasn't rude, he did sound like he was just asking questions to check off boxes on a list and didn't seem very interested in my answers. During the coding portion of the interview, my interviewer offered hints at points where I got stuck.

I thought I did pretty well overall but did not receive an offer to move forward to the next step.

After receiving a generic rejection email, I emailed my recruiter to ask if he could share my interviewer's feedback with me to help me prepare for future interviews. I have not yet received a response, and I don't expect that I will.

Find and return the first duplicate integer in an array.

This should be done in O(n) time and O(1) space.

Assume there will always be at least one duplicated integer in the array.