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I am sorta confused and also could not find a answer online, but in terms of expressive power, .

Non-deterministic FA, PDA, TM 

NFA < NPDA < NTM

Deterministic FA,PDA,TM: This is where i am confused

DFA < PDA < TM?

In a whole: ?

DFA = NFA = e-NFA = RE < DPDA < NPDA = NCFL = DCFL < NTM = DTM?

Please correct me or am i correct?

Sudeep Baniya
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  • @sungyong Thanks for the edit, now help me out :] – Sudeep Baniya Dec 14 '17 at 03:00
  • I'm not sure what you mean by NCFL and DCFL, but if you replace those two with just "CFG" then what you have is correct, where `=` means "is as powerful as" and `<` means "is less powerful than". – Patrick87 Dec 14 '17 at 13:25

1 Answers1

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DFA < PDA < TM is correct.

Remember that DFA = NFA = RegEx in power, every NFA can be converted to a DFA which can be converted to RegEx and the other way around.

Context free languages are a little different. PDA ≠ NPDA. You can construct PDA's for a subset of the context free languages, but you can construct an NPDA for any context free language.

Turing Machines, deterministic and non-deterministics, have equally powerful. Remember that you can simulate any NTM using a single tape DTM.

So in a whole, DFA = NFA = e-NFA = RE < DPDA < NPDA = NCFL = DCFL < NTM = DTM is the correct intuition.

TIZ
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