This is a duplicate of https://www.codewars.com/kata/5efdde81543b3b00153e918a (except initial table derivation. Also there's a decode, but it's trivially similar to encode anyway, so it's not really different)

Duplicate.

Fixed the descriptions

Fixed

Works like a charm now.

Thanks for an interesting kata! Maybe I'll find some time to translate it.

Thanks for posting! I think I've corrected the issue. Could you try re-running the tests, please?

The random tests give me the following error:

 `block in 
': undefined method `prepare_encode' for # (NoMethodError)
	from `times'
	from  `
'

Description should specify the case of multiple 9s between two 7s (79997).

Ordering should be removed from the description.

Unclear about the usage of the block argument. An example and a few test cases would clarify that!

No, it's correct. I think you're confusing permutation with variation. When doing permutation you only rearrange the items, so you can't use an item twice.

Hey! Check out jsperf.com, that's exactly what you're looking for! I've just checked this solution against my own (http://jsperf.com/regexpsplice). It was nearly the same in Chrome, but regexp seems to be slower in FF (on Linux x86).

Very nice solution by the way! (: