How to find the distance between vertices in a tree?

Question

Python

Friends, hello! I can't guess, how can I find out the distances between two entered vertices in the tree using DFS? (The tree is undirected and unweighted)

For example from the picture:
The distance between 0 and 15 is three.

Answer 1

For such business BFS is more convenient.
When adding nodes to the queue, just add the distance to the same place (if the current processed node has a distance of N, then the children in the queue get N + 1)

Answer 2

Your tree must be undirected. Just a list of neighboring vertices for each. And there, run DFS or BFS from one vertex, which counts the distance and displays it if you have reached the second vertex.