Google

First, I received a phone call from the recruiter to schedule the live coding interview. The live coding interview was to be conducted in the language of my choice. I chose Javascript. Unfortunately, I did not get through the live coding phase.

Great – very easy. The team was great, and I was thrilled to be offered a position at the top shop on the block. Unfortunately, I could not attend the fine establishment.

It is hard, and you should review data structures and algorithms for that. This is my personal opinion. Don't believe it 100%; try to figure it out by yourself.