Lowest Common Ancestor of a Binary Search Tree

Source

• leetcode: 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

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        while((root.val-p.val)*(root.val-q.val)>0){
            root = root.val<p.val? root.right: root.left;
        }
        return root;
    }
}