My undergrad was in computer science, although I would say this wasn't the case for most of my classmates. There were a lot of students from other engineering fields (like Mech E or civil), Math, Stats, physics, bio, and business.
Edit: for the Master's degree.
I am happy to give more targeted advice on grad school. Please send me an email at andrew [at] mrdrozdov.com.
https://gist.github.com/mrdrozdov/bd523362210892e6a4e11eb575...