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.

 题目含义：给定一棵二叉树，寻找其中两个给定节点的最近公共祖先（LCA）。

1     public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
2         while (true)
3         {
4             if (root.val > Math.max(p.val,q.val)) root = root.left;
5             else if (root.val < Math.min(p.val,q.val)) root = root.right;
6             else break;
7         }
8         return root;        
9     }