Super tough tech screen. Be prepared.

I was reached out by a recruiter and had a phone call to schedule the tech screen. The interviewer was nice, but they don’t really go over your background or ask about you during the call. It’s straight to the code, so expect that.

The problems were as follows:

1. Given a string word and a string order, sort word according to order. For example, given word "ABBCC" and order "CBA", the result should be "CCBBA". I used a HashMultiset of Character and iterated over the input. Then I iterated over the order and added the count from the set for each character. It was not too difficult.

2. The second problem was to do the columns of a binary tree, and the columns should also be in top-down order. The final result is a list of the nodes' data in that order. Honestly, I had no clue how to solve that. I tried doing a traversal, fitting each node by putting its row and column into a map, and then finally building up the list by sorting on the column.

Please see above.

Tree traversal and sorting