Without being sarcastic, you most likely have a chicom alloy seatpost on that bike. You are lucky you didn't have an injury accident when it broke. Don't replace with the exact same thing. Best bet would prob be for you to take the broken post + bike + seat to a bike co-op or bike shop and see if they have a replacement. Doesn't have to be new or fancy, but not dangerously cheap like the one that broke. Regular post, not a suspension would be fine. The handlebar and stem may be sketchy as well.