Program for this output

Question

A B C D E F E D C B A
A B C D E E D C B A
A B C D D C B A
A B C C B A
A B B A
A A

Answer 1

https://code.sololearn.com/cFqQhVy4LFL4/?ref=app

Answer 2

There you go, one-liner.

https://code.sololearn.com/ce12thQNbT8B/?ref=app

Answer 3

https://code.sololearn.com/c86BYD99fRcp/?ref=app

Answer 4

thank you