Your solution must not modify the original array.

In general, unless you're specifically told to modify an array that was passed as an argument, you shouldn't.

Awesome. The biggest thing I learned is when you start to get frustrated, step away and look at it differently. This one was passing my 'limited' testing and failed the submit - so the more frustrated I got, the more 'hacked' my solution became. :)
Thanks for spending the time to explain and illuminate where I should have done things differently.

It is inspiring to see solutions like this. It is also extrememly informative! Awesome.