Longest Substring Without Repeating Characters (Python)

Validate Binary Search Tree (Python)

kitt posted @ 2014年2月10日 18:22 in LeetCode , 2722 阅读

看到了用左右边界的做法，犀利啊！我感觉思考这道题的时候不要关注tree，而要关注node。

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    # @param root, a tree node
    # @return a boolean
    def check(self, Min, root, Max):
        if root == None: 
            return True
        if not Min < root.val < Max: 
            return False
        return self.check(Min, root.left, root.val) and self.check(root.val, root.right, Max)
    
    def isValidBST(self, root):
        infinity = 10 ** 10
        return self.check(-infinity, root, infinity)