4
$\begingroup$

Let $$ PAL = \lbrace x \in \lbrace 0, 1, \# \rbrace^* | x = rev(x) \rbrace $$ How do I show that a turing machine deciding $PAL$ must use space $\Omega(\log n)$?

I have a feeling that I need to use crossing sequences when crossing the middle of the input tape, but I'm not sure how to relate that to space.

$\endgroup$
1
$\begingroup$

Hint: A Turing machine running in space $S$ runs in time at most $\exp S$.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.