LinkedIn Test Engineer UI & Mobile interview questions

I applied online via LinkedIn, and the recruiter contacted me for an initial touch base and setup the first phone screen. The interview wasn't tough. There were 2 senior engineers who asked couple of test downtime questions. And then came the Coding part, where i was asked to print a level order of a binary tree in a tree format. I solved the first part of the problem with a recursive approach in 2 minutes, but got stuck on printing it like a tree, as the recursive approach made it more difficult to put the line breaks at right places. The interviewer was giving hints, but it was already too late and then i was asked to write sample test cases for the same. After couple of days got an email from HR that i didn't pass the screen. But would definitely recommend the company and wish All the best for future employees!!