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Balanced Binary Tree

Problem statement​

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

My 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) {
    let isBalanced = true
    function dfs(node) {
        if (!node) {
            return 0;
        }
        
        const left = dfs(node.left)
        const right = dfs(node.right)
        
        if (Math.abs(left - right) > 1) {
            isBalanced = false;
        }
        
        return 1 + Math.max(left, right)
    }
    dfs(root)
    
    return isBalanced;
};