<p>Given a binary tree, determine if it is height-balanced.</p> <p>For this problem, a height-balanced binary tree is defined as:</p> <blockquote> <p>a binary tree in which the left and right subtrees of <em>every</em> node differ in height by no more than 1.</p> </blockquote> <p> </p> <p><strong>Example 1:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_1.jpg" style="width: 342px; height: 221px;" /> <pre> <strong>Input:</strong> root = [3,9,20,null,null,15,7] <strong>Output:</strong> true </pre> <p><strong>Example 2:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_2.jpg" style="width: 452px; height: 301px;" /> <pre> <strong>Input:</strong> root = [1,2,2,3,3,null,null,4,4] <strong>Output:</strong> false </pre> <p><strong>Example 3:</strong></p> <pre> <strong>Input:</strong> root = [] <strong>Output:</strong> true </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li>The number of nodes in the tree is in the range <code>[0, 5000]</code>.</li> <li><code>-10<sup>4</sup> <= Node.val <= 10<sup>4</sup></code></li> </ul>