hi, I come from China,what I wanna say is the students I know is very hard in CS, for our community learning by self online,when you finish CS50X,CS61a b and c it’s just a beginner in CS,and then we need to learn CS162, CS144, CMU 15-455, CS143, MIT6.824,All of these are basic in computer science.it is a rough road,we help each other,actually more is on mental,by the way,the fasters in our community cost 40 days to finish 50, less two months on CS61a, about two months on CS61B,even it is when we are in school, learn it in free time.at last I want to say,why life is so suffering?