public class Solution
extends Object
110 - Balanced Binary Tree\.
Easy
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:**
**Input:** root = [3,9,20,null,null,15,7]
**Output:** true
**Example 2:**
**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