I've implemented the Online-DFS-Agent on page 126 in the international
edition. However, the algorithm gets stuck.
After debugging, I found that the problem was while backtracking.
I think the line on the pseudo-code "if s is not null then do" should be
"If s is not null and not backtracking then do". After I change it in my
code everything works properly. Otherwise after the first backtracking
(one state back) it will go again to the last state, then backtracking
again, and so on.
Is it an errata in the pseudo-code of the book or I'm missing