1 /**
2 * Definition for binary tree
3 * struct TreeNode {
4 * int val;
5 * TreeNode *left;
6 * TreeNode *right;
7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {}
8 * };
9 */
10 #include <limits.h>
11 class Solution {
12 public:
13 bool isValid(TreeNode * node, int min, int max){
14 if (node==NULL)
15 return true;
16 if (node->val >= max || node->val <= min)
17 return false;
18 return isValid(node->left, min, node->val) && isValid(node->right, node->val, max);
19 }
20 bool isValidBST(TreeNode *root) {
21 // IMPORTANT: Please reset any member data you declared, as
22 // the same Solution instance will be reused for each test case.
23 return isValid(root, INT_MIN, INT_MAX);
24 }
25 };
