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
Solution:
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @return {boolean}
*/
var isBalanced = function(root) {
if (root === null) return true;
const res = [true];
height(root, res);
return res[0];
};
function height(root, res) {
if (root === null) return 0;
const l = height(root.left, res);
const r = height(root.right, res);
if (Math.abs(l - r) > 1) res[0] = false;
return Math.max(l, r) + 1;
}