I secured a first-round interview through a school career fair. The first-round interview was technical from the start. It began with a request for a brief introduction about myself, and then immediately transitioned to coding.

I was given a piece of paper and asked to code live. The questions primarily focused on data structures and anything I had listed on my resume. The interviewer hopped from topic to topic based on what I indicated I knew.

The second round was also very technical, lasting almost three hours and proving quite intensive.

Define an algorithm that, given a string of words, will be able to sort and find the most common occurrences of subsequent characters.