[StavrosK]

I'm glad that you like my solution, but please note that, as another commenter said, it's a buggier version of the original regex I thought of ("^(dict|here)+$"), which I think should work but doesn't, at least not in Python.

I suspect it's because the match group is being replaced with the last match rather than added as another group, but it will work as a state machine, and is pretty much equivalent to the backtracking example in the article (although with much less code, and no memoization).

That said, I think that the reason interviewers ask about functions for which we have well-known implementations is to see whether or not you know how they work and/or could implement them yourself. Nobody will reasonably expect you to implement your own string comparison routine, but you could score points if, for example, you said Boyer-Moore for string searching rather than the naive iterative version.

[Daniel_Newby]

Nobody will reasonably expect you to implement your own string comparison routine, ...

Standard string comparisons exit on the first mismatched character, which is insecure.

[StavrosK]

Insecure how?

[Daniel_Newby]

Timing attacks. If one of the strings is supplied by the client and the other string is a secret, a comparison that exits at the first mismatch is faster. The client can try every value of the first character until it finds one that takes longer, and it knows that that one is the first character of the secret. It can repeat this with the second character, and so on until the entire secret is known.

[StavrosK]

Interesting, thanks.