I was asked a technical question on Machine Learning during recruiting at a Career Fair, straight away while reviewing my resume. The question was on the possibility of separating houses for a Realtor into various clusters.

I answered by proposing a Decision Tree (ID3 Algorithm) or a Linear Separator, depending on the number of features the test data had.

I was then offered a phone interview, where I was asked a standard question regarding Data Structures and Algorithms (I can't share the details, sorry).

The question regarding Data Structures was difficult because, at best, I could achieve a runtime of O(kn) or O(n log n). However, that wasn't close enough to the desired O(n).