Mmm... What you said between "unless" and the 1st mention of "graph" is correct. But your code needs to be efficient. Please modify your post after reading this, then my note will be spoiler-less to others :)

Hi TS, glad to get your note. The shortList contains all letters required to determine the final answer. In some case, one letter is used twice, the shortList will contain this letter twice. As the result, a short string ends with a longer shortList. But some input like "RGBRGBRGBR" has a shortList with 2 letters.

Got it. That is true. thsnk you

A unique Kata!

It' designed in a very innovative way. More code warriors should try it (1 more to be approvable I guess :> )

One suggestion: How about note the number of tests in the description?

Awesome new description. 10x better than the previous one.
Thank you!

This is awesome! A great demo! You did it.

Please make a video. I have not seen any tesseract video as hardcore as this on Youtube.

Thank you sir