Lowest common ancestor of a Binary Tree

Lowest common ancestor between two nodes n1 and n2 is defined as the lowest node in the tree that has both n1 and n2 as descendants.

Finding lowest common ancestor

Consider the tree:

Lowest common ancestor of nodes with value 1 and 4 is 2

Lowest common ancestor of nodes with value 1 and 5 is 3

Lowest common ancestor of nodes with value 2 and 4 is 4

Lowest common ancestor of nodes with value 1 and 2 is 2