First Common Ancestor of a Binary Tree

问题

If I have a binary search tree like this then what will be lowest common ancestor of nodes 6 and 1?

回答1:

According to the Wikipedia definition of the Lowest common ancestor I correct myself:

The lowest common ancestor (LCA) is a concept in graph theory and computer science. Let T be a rooted tree with n nodes. The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).

So yes going by this definition the correct answer would be 6. If this is an interview question would be good to clarify in advance with the interviewer.

来源：https://stackoverflow.com/questions/10133332/first-common-ancestor-of-a-binary-tree