# Challange
you have one list of numbers like : (1,2,3) with no fixed length ( could contain 1 or 10000 ) itams.

Want to have a funktion that forfills the following requirements:
- give you all possible kombinations in one list back
- No  Duplicates in direct order like (123112) double a number like that is prhibitit.
- No  Duplicates il lager sections like (12 123 123 12)

an example of an possible Result:

(1,3,1,2,3,2,1)
build an algorythem that crate an list as defined wiht as less computional steps as possibe.

# How to use that?
you can commit any solutions in any programming language.
or a formalisation of the problem or idea.