Leetcode 235 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.

Solution 1: since it is BST, it can be found with O(logn)

 public class Solution {  
   public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {  
     TreeNode x=root;  
     while (x!=null) {  
       if (x.val<p.val && x.val<q.val) x=x.right;  
       else if (x.val>p.val && x.val>q.val) x=x.left;  
       else return x;  
     }  
     return x;  
   }  
 }