enter image description here

I am studying PDA at the moment, and I came up with this question.

The figure above tells me that although both PDA accept the same language, one is non-deterministic and the other is deterministic. I don't understand the reason why the first one in non-deterministic. As far as I know, the conditions for DPDA is that

1) every transition should have at most one move

2) if $\delta$(q,a,X) is not empty, then $\delta$(q,$\epsilon$,X) should be empty.

However, since the first PDA does satisfy the above conditions therefore I thought it is DPDA.

What am I missing?

Thanks in advance.

  • 2
    $\begingroup$ Please don't use images as crtitical content of your post. This makes your question harder to search and inaccessible to the visually impaired; we don't like that. Please transcribe text and mathematics (note that you can use LaTeX) and don't forget to give proper attribution to your sources! $\endgroup$
    – D.W.
    Jan 5, 2016 at 3:10

1 Answer 1


The first PDA doesn't comply the second condition because $|\delta (q0,a,\epsilon)| = |\delta (q0,\epsilon,\epsilon)| = 1$.


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