Alan Belmont Cobham was an American mathematician and computer scientist known for inventing the concept of polynomial time and the complexity class P,[B] for Cobham's thesis stating that the problems that have practically usable computer solutions are characterized by having polynomial time,[B] and for Cobham's theorem on the sets of numbers that can be recognized by finite automata.[C] He also did foundational work on automatic sequences,[D] invented priority queues and studied them from the point of view of queueing theory,[A] and wrote a program for playing contract bridge that was one of the best in the world during the mid-1980s.