That's not the downside. It follows the rules and could be "fixed" for other situations.

The real downside is Linq. It's slow and harder to read and maintain.

My code would be simple to adapt to any number of consecutive digits while being about twice as fast in execution.

Linq might have it's uses, I just haven't found any yet...

Yet more slow Linq. Why?

I can follow this now. It's interesting to come back to this 7 years later, it makes much more sense to me now.

One line. Excellent!

I used almost the same approach, passed tests under Attempt button and was happy it's done.
Yes, I thought about "what if first element will be default?"
The answer depends on environment we work in:

• If we're talking about real TDD production - I can say it counts as solution because tests passed. If tests were not designed to check this case - ask the guy who wrote these test. No need to fill code with garbage checks for everyting. If it will break somehow - we'll see an exception, fix tests, fix the code to pass tests. Happy end.
• If we talk about unpredictable startup thing where you really don't know what to expect and have no tests - yes you all are right, we have to think about it.

You may just return false withut var rez. And in if construction return true

watafuk bro

Just when I thought that one line is impossible.