Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.

According to the definition of LCA on Wikipedia: “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).”

    _____6______
   /            \
 ___2__       ___8__
/      \     /      \
0      _4   7       9
      /  \
      3   5

For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.

Java

http://articles.leetcode.com/2011/07/lowest-common-ancestor-of-a-binary-search-tree.html

public class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root == null || p == null || q == null) {
            return null;
        }

        if(Math.max(p.val, q.val) < root.val) {
            return lowestCommonAncestor(root.left, p, q);
        } else if(Math.min(p.val, q.val) > root.val) {
            return lowestCommonAncestor(root.right, p, q);
        } else {
            return root;
        }
    }
}