[Solved] 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.

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Question

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.

Example 1:

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Input: root = [3,9,20,null,null,15,7]
Output: true

Example 2:

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Input: root = [1,2,2,3,3,null,null,4,4]
Output: false

Example 3:

Input: root = []
Output: true

Constraints:

  • The number of nodes in the tree is in the range [0, 5000].
  • -104 <= Node.val <= 104

Python 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

def height(root):
    global isBal
    if not root: return 0
    lh = height(root.left)
    rh = height(root.right)
    if abs(lh-rh)>1:isBal= False
    return 1+max(lh,rh)
    
class Solution:
    def isBalanced(self, root: TreeNode) -> bool:
        global isBal
        isBal = True
        height(root)
        return isBal

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