It's a bit more complicated than that for non-residential buildings over a small size. Any emergency exits and doors for an area where a large group of people

It's a bit more complicated than that for non-residential buildings over a small size. Any emergency exits and doors for an area where a large group of people might aggregate (i.e. a classroom) almost always have to open outward because mobs are the biggest problem in an emergency. Emergency exits also generally have to be equipped with a crash bar and other hardware (such as auto-closing arms). Inward opening doors are frequently problems in emergencies. People get smashed up against them by a mob and are unable to open it. Generally though, bathrooms and other interior doors that do not open to a path of egress can do whatever is most convenient for the location and use. If you want to minimize the amount of time required for a building to vacate, you want as many doors to open outward toward the path of egress as possible. Residential buildings have entirely different constraints (and the code for hallway width / obstructions is vastly different).