If you are applying for the Android course: No, you can use either a Mac or Windows machine.
If you are applying for the iOS class: Yes, you need a Mac machine.
iOS development requires Xcode which requires MacOS. Labs and assignment app projects require 5-10+ hrs in Xcode each week. This is an important consideration if your primary access to a Mac comes from a computer lab or friend.
It is, however, possible to run Xcode using a virtual machine on a PC. If you decide to go this route, you will be solely responsible for handling everything that goes along with using a VM. We also recommend that you set up the VM as early as possible to ensure that you’re ready before the semester begins.