Did you consult wikipedia or search for other algorithms?

Many sources recommend an algorithm from Frank Ruskey , easily found implemented in various languages, here one in Python De_Bruijn_sequence#Algorithm which is not too hard to be ported.

Besides: The minimal length k^n is proven to be always achievable.

Which consequently means at least your first result and hence your algorithm is wrong.

update
De Bruijn is supposed to be cyclic!

AAACCCBCCACBBCBACABCAABBBABAA

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!

In reply to Re: Generic De Bruijn Sequence by LanX
in thread Generic De Bruijn Sequence by QM

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