# LeetCode 110Balanced Binary Tree

## LeetCode 110 Balanced Binary Tree Problem

``````# 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
"""
# Bottom-up recursion with sentinel -1
if root is None:
return True
if self.getDepth(root) < 0:
return False
return True

def getDepth(self, node):
if node is None:
return 1
ld = self.getDepth(node.left)
if ld < 0:
return -1
rd = self.getDepth(node.right)
if rd < 0:
return -1
elif abs(ld - rd) > 1:
return -1
else:
return max(ld, rd) + 1

# https://discuss.leetcode.com/topic/7798/the-bottom-up-o-n-solution-would-be-better
# def isBalanced(self, root):
#     # Top-down recursion
#     if root is None:
#         return True
#     left = self.depth(root.left)
#     right = self.depth(root.right)
#     return abs(left - right) <= 1 and self.isBalanced(root.left) and self.isBalanced(root.right)

# def depth(self, root):
#     if root is None:
#         return 0
#     return max(self.depth(root.left), self.depth(root.right)) + 1

``````

## List of all Balanced Binary Tree problems

Leetcode 110 Balanced Binary Tree problem solution in python3 with explanation. This is the best place to expand your knowledge and get prepared for your next interview.

self.val = x

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