I posted such a photo in space, and my classmate found my house with this photo and knocked at the door. It's terrible. How did he do it?

It's actually quite simple. You can tell the location of your home by the trees and sunshine outside the window. Then according to his general location of your home, you can know which community you live in by searching all directions of your general location through Baidu. Your friend must know your name or the name of your real estate agent, and then you can know which floor and room you live in, and then you can ask where the real estate is, or you can ask by courier.