It is said that there is no accommodation in Huanglong.

There is the Hualong Hotel at the entrance of the scenic area. You are suggested to make the reservation before visiting in case there is no room left when you get out.

You can also spend a night in Songpan where you can have more choices and the charge can be more reasonable. I heard the buses to Songpan don't have fixed departure time, you may need to check the schedule in advance. Or, just charter a car at the gate of the scenic area to Songpan.