Re: Cardinality of P
On 20 Aug., 00:18, "the.theorist" <the.theor...@xxxxxxxxx> wrote:
Does anybody know what the cardinality of the set P is?
what about the cardinality of NP?
I'll try to give an answer, and hope that others will point out if I
am wrong.
P is the set of all languages that can be decided by a Turing machine
in polynomial time. The cardinality of that set is countable infinite,
or aleph 0, if you will. It is infinitely large, as the languages L_1
= {1}, L_2 = {2}, ... (i.e., the languages that consists of a single
number) are in P. It is countable infinite, as each of the languages
in P can be assigned a natural number (e.g., the smallest Goedel
number of a Turing machine that decides the language). The same holds
for NP, and any other complexity class that is defined by a runtime
complexity bound on Turing machines.
.
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