Science Fair Project Encyclopedia
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.
See computation for a chart showing which classes are subsets of other classes.
Many of these classes have a 'Co' partner which consists of the complements of all languages in the original class. For example if L is in NP then the complement of L is in Co-NP. (This doesn't mean that the complement of NP is Co-NP - there are languages which are known to be in both, and other languages which are known to be in neither.)
If you don't see a class listed (such as Co-UP) you should look under its partner (such as UP).
| #P | Count solutions to an NP problem |
| #P-complete | The hardest problems in #P |
| AM | Solvable in polynomial time by an Arthur-Merlin protocol |
| BPP | Solvable in polynomial time by randomized algorithms (answer is probably right) |
| BQP | Solvable in polynomial time on a quantum computer (answer is probably right) |
| Co-NP | "NO" answers checkable in polynomial time |
| Co-NP-complete | The hardest problems in Co-NP |
| DSPACE(f(n)) | Solvable by a deterministic machine in space O(f(n)). |
| DTIME(f(n)) | Solvable by a deterministic machine in time O(f(n)). |
| E | Solvable in exponential time with linear exponent |
| ELEMENTARY | The union of the classes in the exponential hierarchy |
| ESPACE | Solvable in exponential space with linear exponent |
| EXP | Same as EXPTIME |
| EXPSPACE | Solvable in exponential space |
| EXPTIME | Solvable with exponential time |
| FNP | The analogue of NP for function problems |
| FP | The analogue of P for function problems |
| FPNP | The analogue of PNP for function problems; the home of the traveling salesman problem |
| FPT | Fixed-parameter tractable |
| IP | Solvable in polynomial time by an interactive proof system |
| L | Solvable in logarithmic (small) space |
| MA | Solvable in polynomial time by a Merlin-Arthur protocol |
| NC | Solvable efficiently (in polylogarithmic time) on parallel computers |
| NE | Solvable by a non-deterministic machine in exponential time with linear exponent |
| NESPACE | Solvable by a non-deterministic machine in exponential space with linear exponent |
| NEXP | Same as NEXPTIME |
| NEXPSPACE | Solvable by a non-deterministic machine in exponential space |
| NEXPTIME | Solvable by a non-deterministic machine in exponential time |
| NL | "YES" answers checkable in logarithmic space |
| NP | "YES" answers checkable in polynomial time (see complexity classes P and NP) |
| NP-complete | The hardest or most expressive problems in NP |
| NP-easy | Analogue to PNP for function problems; another name for FPNP |
| NP-equivalent | The hardest problems in FPNP |
| NP-hard | Either NP-complete or harder |
| NSPACE(f(n)) | Solvable by a non-deterministic machine in space O(f(n)). |
| NTIME(f(n)) | Solvable by a non-deterministic machine in time O(f(n)). |
| P | Solvable in polynomial time |
| P-complete | The hardest problems in P to solve on parallel computers |
| PCP | Probabilistically Checkable Proof |
| PH | The union of the classes in the polynomial hierarchy |
| PNP | Solvable in polynomial time with an oracle for a problem in NP; also known as Δ2P |
| PP | Probabilistically Polynomial (answer is right with probability slightly more than ½) |
| PSPACE | Solvable with polynomial memory and unlimited time |
| PSPACE-complete | The hardest problems in PSPACE |
| RL | Solvable in logarithmic space by randomized algorithms (NO answer is probably right, YES is certainly right) |
| RP | Solvable in polynomial time by randomized algorithms (NO answer is probably right, YES is certainly right) |
| RLP | Solvable in logarithmic space and polynomial time by randomized algorithms (NO answer is probably right, YES is certainly right) |
| SL | Problems log-space reducible to determining if a path exist between given vertices in an undirected graph. In October 2004 it was discovered that this class is in fact equal to L. |
| UP | Unambiguous Non-Deterministic Polytime functions. |
| ZPP | Solvable by randomized algorithms (answer is always right, average running time is polynomial) |
External link
- Complexity Zoo - list of over 400 complexity classes and their properties
10-26-2009 08:16:03
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details