Five programming problems every Software Engineer should be able to solve in less than 1 hour

[Geoff Canyon]

https://blog.svpino.com/2015/05/07/five-programming-problems-every-software-engineer-should-be-able-to-solve-in-less-than-1-hour

Interesting blog post, made doubly interesting because when the author
posted his solutions to problems 4 and 5, one of his solutions was
incorrect. So I guess he won't be hiring himself...

In any case, I thought they were interesting so I gave it a shot. I
finished in something like 40 minutes, but I think some of my solutions are
more expedient than I would like.

I'll post the code in replies, so don't read those if you want to try
yourself.