Editing Time complexity (section)

== Exponential time ==
An algorithm is said to be '''exponential time''', if ''T''(''n'') is upper bounded by 2<sup>poly(''n'')</sup>, where poly(''n'') is some polynomial in ''n''. More formally, an algorithm is exponential time if ''T''(''n'') is bounded by ''O''(2<sup>''n''<sup>''k''</sup></sup>) for some constant ''k''. Problems which admit exponential time algorithms on a deterministic Turing machine form the complexity class known as '''[[EXP]]'''.
:<math>\textsf{EXP} = \bigcup_{c \in \mathbb{R_+}} \textsf{DTIME}\left(2^{n^c}\right)</math>

Sometimes, exponential time is used to refer to algorithms that have ''T''(''n'') = 2<sup>''O''(''n'')</sup>, where the exponent is at most a linear function of ''n''. This gives rise to the complexity class '''[[E (complexity)|E]]'''.
:<math>\textsf{E} = \bigcup_{c \in \mathbb{N}} \textsf{DTIME}\left(2^{cn}\right)</math>