235. Lowest Common Ancestor of a Binary Search Tree

代码如下：

/**
 * 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) {

        if(root==null||p==null||q==null)
        return root;

       TreeNode t=root;

       if(Math.max(p.val,q.val)<root.val&&root.left!=null)
       return lowestCommonAncestor(root.left,p,q);
       else if(Math.min(p.val,q.val)>root.val&&root.right!=null)
       return lowestCommonAncestor(root.right,p,q);
       else if(Math.min(p.val,q.val)<=root.val&&Math.max(p.val,q.val)>=root.val)
       return root;

       return root;
    }

}