Yes that's right!

And now ?

I really loved this recursive solution, while not being the efficient one!

I fixed the Issue!

Normally I fixed the Issue!

Normally I fixed the Issue!

Hahaha! That's what I added after getting your request :)

The elements are ordered and added sequentially, meaning arr[1] is generated from arr[0], arr[2] is generated from arr[1] and so on.

How many test could you suggest, please ?

Having a string of six characaters there are cases where there are at most six different permutations it could be lesser.
Exemples :
"ABCDEF" ==> "ABCDEF","FAEBDC","CFDABE","ECBFAD","DEBFAD","DEACFB" and "BDFECA"
"BBBBBB" ==> "BBBBBB"

"MAAMAAA" ==> "MAAMAAA","AMAAAAM" (only two permutations)

Yes Java and Python are more mature. Actually Java is the most efficient of the three of them.

Can you suggest another formulation, please ?

What sc ? I removed it.

That's a typo, dear friend, there are four examples below the description to explain exactly the outcome of the function.

Yes you're right on some extent. But, you compute the indexes once but on the other hand you need more storage :)
An array for the indexes, for a huge string you will need a huge array
I just use a two simple vars that compute the next position each time :)