Looking for fast algorithm to find distance between two nodes in binary tree

Question

How do I find the distance between two nodes in a binary tree? Equivalently, what algorithms are there for finding the most recent common ancestor (lowest common ancestor)

Answer 1

Make two sets consisting of the ancestors of each: while the union of the sets is empty, add the next ancestor of each node to the appropriate list. Once there is a common node, that's the common ancestor.