Validate Binary Search Tree

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.

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool judge(TreeNode* root, int min, int max, bool bmin, bool bmax)    {        if (0 == root) return true;        if (bmin && root->val <= min) return false;        if (bmax && root->val >= max) return false;        return judge(root->left, min, root->val, bmin, true) && judge(root->right, root->val, max, true, bmax);    }    bool isValidBST(TreeNode *root)    {        if (0 == root) return true;        return judge(root, 0, 0, false, false);    }};