How to find adjacent / adjacent cubes using octree datastructure?

I created an octa border for a closed surface. All octree cubes that contain a surface are subdivided to one level. Thus, all nodes of the leaf are of the same size. I need help finding neighbors for each of these terminal cubes. I tried to refer to different docs but couldn't figure out how to actually implement it .. in Matlab. Right now I am treating all terminal cubes as voxel cubes (without using the octet data structure) and using brute force to figure out which of the 26 possible neighbors is in the list of cubes that make up the surface. Age is required to get the result. I am new to programming, so I would really appreciate if someone could suggest ways to find the neighbors of leaf nodes more efficiently and how to implement the method by coding in Matlab. Thank!!