The phone interview consisted of a one-hour pre-screen phone conversation. It started with the interviewer asking basic questions about some of the items listed on my resume. After that, the interviewer delved deeper into some of the projects I worked on and moved on to more specific technical questions about my C++ programming skills. Finally, I was asked a technical brain teaser question.

I was asked to write an algorithm in C++ to sort an array. The function I was to write was to take in a string of letters 'b' and 'r'. Here, 'b' represents a red ball, and 'r' represents a blue ball. The function was to return an integer with the least number of swaps needed to separate the balls by their own colors.

For example, given the input RBBR, the function should return 1. This is because only one swap is needed to arrange the balls into either RRBB or BBRR.