110.balanced-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(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def isBalanced(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        def dfs(p):
            if not p:
                return 0
            
            left = dfs(p.left)
            right = dfs(p.right)
            if left == -1 or right == -1:
                return -1
            if abs(left - right) > 1:
                return -1
            return 1 + max(left, right)
        if dfs(root) == -1:
            return False
        return True