[natdempk]

Is it just me or is his improved solution a possibly incorrect way to solve the second problem? With his solution "aabbcccaa" compresses to "a4b2c3", but I would expect that to compress to in "a2b2c3a2".

Am I misunderstanding the problem here? In the context of compression why would it just be about counting letters? Why wouldn't you just use a hash of character counts if that is all you care about? Don't you want to maintain the form of the string also so you can unpack the original value?