Comscore New Grad Software Engineer interview questions

At first a HR in comscore told me that I will get a phone interview and then go to Virginia headquarters for onsite if I pass the phone interview. But at last I get a final interview just in their Chicago Office in Willis Tower. 4 people one by one came to interview me, one of them is a newly grad student just joined them. The last is a senior manager. They are all very friendly. The questions are about my resume project, they asked me to illustrate one of my project in my resume. They the have white paper to you to write some code. You will use knowledge of trees, recursion, etc, very normal data structure and algorithm questions. One of them asked me to design a class, not very hard. But I didn't figure out some answers asked by the last person, it's not about programming but math.