The concept of entropy pushes one to think of binary trees. Huffman coding used in real compressors use Huffman trees [1] that express the prefix code used to define entropy as in Colah's blog http://colah.github.io/posts/2015-09-Visual-Information/ Entropy is the expected lenght, so it's the weighted sum of the lenght of the paths from root to leaves, weighted by their frequency.

[1] https://www.siggraph.org/education/materials/HyperGraph/vide...