In the movie As Good As It Gets, actor Jack Nicholson plays the character of Melvin Udall, a gifted writer who always eats in the same restaurant, brings his own plastic utensils, and engages in strict patterns of behavior, such as repetitive handwashing or walking carefully on the sidewalk to avoid stepping on a crack. Failure to follow these ritual behaviors results in extreme anxiety and distress. The character Nicholson was portraying would probably be diagnosed with _____ disorder.