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).”

给你一棵二叉树，让你找到两个顶点的最低公共顶点。
很简单，对于公共顶点root。他一定会满足root>二者之中的小者且大于大者，或者说等于两个值之中的一个。那么迭代查找就好了。

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
         while(root!=null)
         {
             if(root.val==p.val||root.val==q.val)
                 break;
             else if(root.val>p.val&&root.val>q.val)
                 root=root.left;
             else if(root.val<p.val&&root.val<q.val)
                 root=root.right;
             else
                 break;
         }
        return root;
    }
    
}