I had a few chats with the recruiter, mostly because I kept dropping off. The recruiter was nice and seemed generally enthusiastic. I finally scheduled a phone screen in July 2017.

I completed the exercise on CollabEdit.

• I completed it within the time allotted, with about 8 minutes to spare.
• I provided correct runtime and functional code.

The interviewer was skeptical it worked, but after walking through it, he decided it did and said I performed pretty well. I was not moved forward to an onsite interview and was not given any feedback on my performance.

I have no idea what went wrong. This is the second time I've done a phone screen with Facebook, and this is exactly what happened before.

Remove unbalanced parentheses from a string.

Provide runtime and space complexity.