leetcode之Validate Binary Search Tree的困惑

[愤怒的菜鸟_]

Given a binary tree, determine if it is a valid binary search tree (BST).

Assume a BST is defined as follows:

The left subtree of a node contains only nodes with keys less than the node's key.
The right subtree of a node contains only nodes with keys greater than the node's key.
Both the left and right subtrees must also be binary search trees.
Example 1:
2
/ \
1 3
Binary tree [2,1,3], return true.
Example 2:
1
/ \
2 3
Binary tree [1,2,3], return false.

/**
 * 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 BST(TreeNode* root, long long left, long long right) {
		if (!root) return true;
		if (root->val<=left || root->val>=right) return false;
		return BST(root->left, left, root->val) && BST(root->right, root->val, right);
	}
	bool isValidBST(TreeNode* root) {
		if (!root) return true;
		return BST(root->left, INT_MIN, root->val) && BST(root->right, root->val, INT_MAX);
	}
};

[-2147483648,null,2147483647]
为什么这个测试用例通不过，自己的vs2015是可以通过的