I am pulling my hair out with this one. I got the cipher part easily enough once I figured out that you were counting spaces as characters for the shift. My problem is trying to split the message into an array. I went through the message, grabbing the number of characters and appending them as an element of a array, then stripping those characters from the front of the string, then get the next sequence of characters. This works fine, sometimes. Sometimes it strips an extra character (or two). For the life of me, I can't figure out why. The length of the string I am stripping is correct. I even though it might be having trouble with spaces, so I tried filling the spaces with a character. Same problem. There has got to be an easier way!

Thanks! I forgot to make sure the input was single digits only. Doh!

OK, I'm stumped. My code passes all the basic tests, but failed two of the random tests. Why are [1,2,3,4] and [1,1] invalid arrays that should return None? They both contain non-negative, single digit integers as specified in the instructions.