Count And Say

Count And Say


Given a string of digits that is guaranteed to contain only digit characters from 0123456789, read that string “out loud” by saying how many times each digit occurs consecutively in the current bunch of digits, and then return the string of digits that you just said out loud.


As silly and straightforward as this count-and-say sequence problem might initially seem, it required the genius of a mathematician of no lesser caliber than the late great John Conway himself not only to notice the tremendous complexity ready to burst out from just below the surface when this operation is repeatedly iterated to produce an infinite sequence of such digit strings, but also capture that whole mess into a symbolic polynomial equation, as the man himself explains in this video.

You can also check out the related construct of the infinitely long and yet perfectly self-describing Kolakoski sequence where only the lengths of each consecutive block of digits is written into the result string, not the actual digits.


Input: String (str).

Output: String (str).


assert count_and_say("333388822211177") == "4338323127"
assert count_and_say("1") == "11"
assert count_and_say("") == ""

The mission was taken from Python CCPS 109. It is taught for Ryerson Chang School of Continuing Education by Ilkka Kokkarinen

Invalid hot key. Each hot key should be unique and valid
Hot keys:
CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

pip3 install checkio_client

Configure your tool

checkio --domain=py config --key=

Sync solutions into your local folder

checkio sync

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

checkio serv -d

Alternatevly, you can install Chrome extension or FF addon

checkio install-plugin
checkio install-plugin --ff
checkio install-plugin --chromium

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

Pair Programming (Beta-version)

Welcome to Pair Programming! Engage in real-time collaboration on coding projects by starting a session and sharing the provided unique URL with friends or colleagues. This feature is perfect for joint project development, debugging, or learning new skills together. Simply click 'Start Session' to begin your collaborative coding journey!

Waiting for Pair Programming to start...

You are trying to join a pair programming session that has not started yet.

Please wait for the session creator to join.

Waiting for Pair Programming to reconnect...

It looks like the creator of the pair programming session closed the editor window.

It might happen accidentally, so that you can wait for reconnection.

<< <
> >>
exec show

Whats Next?

Free accounts will see Best CheckiO solutions with some delay.
Best Solutions will be opened in a moment
Become Awesome and Don't wait
The next stage is ""
Will be activated in
View More Solutions Random Review Solutions Go to the next mission