On q-ary fix-free codes and directed deBrujin graphs

Abstract

We treat here the question, whether there exists a q-ary fix-free code for a given sequence of codeword lengths. We focus mostly on results which establish the 3/4-conjecture of Ahlswede/Balkenhol/Khachatrian for special classes of lengths sequences. We construct fix-free codes with directed deBrujin graphs. We improve and generalize work of Kukorelly/Zeger and of Yekhanin