I was selected for an interview as an intern through my university's co-op program, so the process was fairly quick.

The interview was scheduled five days into the future.

Two days before the interview, all the candidates were invited to a dinner where we were able to meet and chat with our interviewers before the interview the next day.

The interview itself was technical from start to finish. The questions were difficult and tackled data structures, algorithms, time and space efficiency, and HTML and CSS for web design.

You are given an array of N elements in the form "property1: value1; property2: value2; ...; propertyX: valueX;" for some N and any X. There is also another array of M elements of the form "property: value". You are supposed to write an algorithm to remove every element in the N-length array that has a "property: value" pair present in the M-length array.

The trick is that the most intuitive solution of iterating through the M array and filtering the N array at each element is already written. You must come up with a solution that solves the problem in less than O(NM) time.