| 21. | Other methods which backtrack or yield multiple parses may even take exponential time when they guess badly.
|
| 22. | Indeed, it is conjectured for many natural NP-complete problems that they do not have sub-exponential time algorithms.
|
| 23. | In fact, by the time hierarchy theorem, they cannot be solved in significantly less than exponential time.
|
| 24. | NP-hard problems can often be expressed as integer programs ( IP ) and solved exactly in exponential time.
|
| 25. | The exponential time hypothesis also implies that any fixed-parameter tractable algorithm for double exponential dependence on the parameter.
|
| 26. | And, listing all maximal cliques may require exponential time as there exist graphs with exponentially many maximal cliques.
|
| 27. | In January 2017, Babai shortly retracted the quasi-polynomiality claim and stated a sub-exponential time time complexity bound instead.
|
| 28. | Even so, this is a quite satisfactory method, considering that even the best known algorithms have exponential time growth.
|
| 29. | However, this takes exponential time.
|
| 30. | This gap was closed in 1978 by Vaughan Pratt who showed that PDL was decidable in deterministic exponential time.
|
