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# Time: O(n)

# Space: O(h), h is height of binary tree

#

# Given a binary tree, determine if it is height-balanced.

#

# For this problem, a height-balanced binary tree is defined as a binary tree

# in which the depth of the two subtrees of every node never differ by more than 1.

#

# Definition for a binary tree 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 isBalanced(self, root):

return (self.getHeight(root) >= 0)

def getHeight(self, root):

if root is None:

return 0

left_height, right_height = self.getHeight(root.left), self.getHeight(root.right)

if left_height < 0 or right_height < 0 or abs(left_height - right_height) > 1:

return -1

return max(left_height, right_height) + 1

if __name__ == "__main__":

root = TreeNode(0)

root.left = TreeNode(1)

result = Solution().isBalanced(root)

print result

root.left.left = TreeNode(2)

result = Solution().isBalanced(root)

print result