leetcode - Validate Binary Search Tree

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
#include <limits.h>
class Solution {
public:
bool isValid(TreeNode * node, int min, int max){
if (node==NULL)
return true;
if (node->val >= max || node->val <= min)
return false;
return isValid(node->left, min, node->val) && isValid(node->right, node->val, max);
}
bool isValidBST(TreeNode *root) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
return isValid(root, INT_MIN, INT_MAX);
}
};