That's great. Now, go to their homepage without being logged in and see if you can find a link anywhere to the all-questions page.

Only by using "view source":

            <!--
            <li>
                <a href="/all-questions">All Questions</a>
            </li>
            -->

Note that they've commented out the link for some reason.

Hrm. Maybe that's one of the interview questions.

He's talking about the normal flow of the site (click the big blue button at the bottom of the first page, then the second page). This leads to a "Login with Github/Google/Facebook" prompt that can't be skipped. You can close it, but that doesn't get you anywhere.

I would guess that obituary_latte is talking about the fact that there's no link to the page you're referring to.

Worst part is their max-stack isn't optimal. You can do it with O(1) additional space.

Please explain. Without maintaining that ordering, you're going to have to iterate over the entire stack after every pop, no? One of their requirements was to keep pop() at O(1) rather than O(n).

Hm. How?