leetcode : valid binary search tree

不能通过 当元素中 有 val == INT_MAX 或者  val == INT_MIN 

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isValidBST(TreeNode* root) {
        if(root==NULL) return true;
       return  isv(root,INT_MIN,INT_MAX);
    }
    bool isv(TreeNode * root , int min ,int max)
    {
        if(root==NULL) return true;
        if(root->left!=NULL &&( root->val<= root->left->val||root->left->val<=min))  return false;
        if(root->right!=NULL&&( root->val>=root->right->val||root->right->val>=max))  return false;
         return isv(root->left,min,root->val)&&isv(root->right,root->val,max);
    }
};