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 left and right subtrees of every node differ in height by no more than 1.

xample 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7

Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4

Return false.

Solution

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    
    def get_height(self, node):
        if node == None:
            return 0
        return 1 + max(self.get_height(node.left), self.get_height(node.right))

    def isBalanced(self, root: Optional[TreeNode]) -> bool:
        if root == None:
            return True
        
        left_h = self.get_height(root.left)
        right_h = self.get_height(root.right)
        
        if abs(left_h - right_h) >= 2:
            return False
        
        return self.isBalanced(root.left) and self.isBalanced(root.right)