I think for time complexity you always have to consider worst case scenario, so in this case short circuiting would help practically, but for calculating time complexity I don't think it does.

I should have used recursion :(

Recursively calling itself....duh!

You're iterating many times over the same data. I assume this is because you're trying not to make any assumptions about the shape of the data, but the spec did say the numbers would always be in order.

I could break your code r = "123 S OH 43235 Street Columbus OH 43221", zipcode = "OH 43235"

you could clean up your code (and avoid regex, if you so choose) by using String#partition, which is essentially like a split that only splits on the first instance of the separator. This would give you the numbers and the rest in one method call.

nice and direct

What's with extra % 2? Was there a reason behind it?