Challenge: File compression and "run-length encoding"

Question

This challenge is meant to explore the basic idea behind file compression using a very naive type of compression called "run-length encoding".

The idea behind run-length encoding is to take a string and replace
all repeated sequences of characters with the number of times that character is repeated followed by that character.

For example, we'd encode the string:

WWWWWWAAAAAAWWWWWWAAAAAABBBBBB

as:

6W6A6W6A6B

As you can see, this "encoded" string is actually *shorter* than the input
string but still contains all the information we need to reconstruct the
original.

On the other hand, the string "ABCEDFG" would be encoded as:

1A1B1C1D1E1F1G

More info:
http://en.wikipedia.org/wiki/Run-length_encoding

* Make a program in any language(s) you want, to encode a string using run-length encoding.

* Bonus: Make a decoder, also.

Answer 1

My try:
https://code.sololearn.com/WXVGnOSS20tE/?ref=app

Answer 2

I wrote a second version to solve a problem you can have in this challenge: when encoding a string containing numbers you can have a decoding error (if you want to write a decoder..).
for example if you encode '11111111111222222222222' you get '111122', but decoding '111122' you get '1122' that is different from the initial string.
My second version introduces a new symbol ('.', but you can change it if you want) to separate the counter from the counted numbers so that if you encode '11111111111222222222222' you get '11.112.2' and the decoder can read "there are eleven 1's and twelve 2's" and give you back the right string... try it! 🐍
https://code.sololearn.com/cbBX8YFIqykh/?ref=app

Answer 3

my try non Python 🐍
https://code.sololearn.com/crz83IJRo63t/?ref=app

Answer 4

https://code.sololearn.com/cqmDOpiuIGPI/?ref=app

Answer 5

(Has a decoder also!)
https://code.sololearn.com/ci8952fT2JVs/?ref=app

Answer 6

https://code.sololearn.com/cID50SHkvGo5/?ref=app

Answer 7

my practice on python https://code.sololearn.com/cOU95o2TsnSs/?ref=app

example, input: aaabbc:encode
result: 3a2b1c
and input: 3a2b1c:decode
output: aaabbc

Answer 8

Dude, this one was really hard, follow my answer.
https://code.sololearn.com/coHIa7tHW6Qx/#py