【leetcode刷题】T112-验证二叉搜索树

示例 :
输入:
    
   / \
     
输出: true
    
示例 :
输入:
    
   / \
     
     / \
       
输出: false
解释: 输入为: [,,,null,null,,]。
     根节点的值为  ，但是其右子节点值为  。

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def isValidBST(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        return self.isValid(root, sys.maxsize, -sys.maxsize)
        
    def isValid(self, root, max0, min0):
        if not root:
            return True
        if root.val >= max0 or root.val <= min0:
            return False
        return self.isValid(root.left, root.val, min0) and self.isValid(root.right, max0, root.val)

/**
 * 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) {
        return isValidBST(root, LONG_MAX, LONG_MIN);
    }
    bool isValidBST(TreeNode* root, long max0, long min0) {
        if(!root)
            return true;
        if(root->val >= max0 || root->val <= min0)
            return false;
        return isValidBST(root->left, root->val, min0) && isValidBST(root->right, max0, root->val);
    }
};