List of complexity classes
This is a list of complexity classes in computational complexity theory. For other computational and complexity subjects, see list of computability and complexity topics.
Many of these classes have a 'co' partner which consists of the complements of all languages in the original class. For example if a language L is in NP then the complement of L is in co-NP.
"The hardest problems" of a class refer to problems which belong to the class such that every other problem of that class can be reduced to it. Furthermore, the reduction is also a problem of the given class, or its subset.
