I spent 20 minutes debugging this, before realizing one of the tests I added had a typo... Not really a hard kata

I feel this is a great idea. I would love to be able to search for a specific class of problems and go through them form easy to hard without jumping to different stuff.

This. I was actually looking for the time performance of other solutions compared to mine, but the only solution I had found was actually implementing all of them and time them myself.

The C# requires the addition of using System; at the beginning else it won't compile.