Generalized Huffman Coding for Binary Trees with Choosable Edge Lengths

In this paper we study binary trees with choosable edge lengths, in particular rooted binary trees with the property that the two edges leading from every non-leaf to its two children are assigned integral lengths $l_1$ and $l_2$ with $l_1+l_2=k$ for a constant $k\in \mathbb{N}$. The depth of a leaf is the total length of the edges of the unique root-leaf-path. We present a generalization of the Huffman Coding that can decide in polynomial time if for given values $d_1,\mathrm{.}\mathrm{.}\mathrm{.},d_n\in {\mathbb{N}}_{\ge 0}$ there exists a rooted binary tree with choosable edge lengths with $n$ leaves having depths at most $d_1,\mathrm{.}\mathrm{.}\mathrm{.},d_n$.