I wish the words "Huffman Tree" would go away entirely. Huffman, as used in the past 40 years, actually describes a scheme commonly called "Canonical Huffman"[0] that can be constructed entirely without a tree. ryg recommends reading this paper on it [1], and I wholeheartedly agree. Other than that, great article!
[0] https://en.m.wikipedia.org/wiki/Canonical_Huffman_code [1] https://pdfs.semanticscholar.org/bda3/442cc6b1d10e4b36b574af...