55-II-isBalanced.js

/**
 * https://leetcode-cn.com/problems/ping-heng-er-cha-shu-lcof/
 * 面试题55 - II. 平衡二叉树
 * Easy
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isBalanced = function(root) {
    if(!root) return true
    if(!isBalanced(root.left) || !isBalanced(root.right)) return false
    if(Math.abs(getDepth(root.left)-getDepth(root.right)) > 1) return false
    return true
};

function getDepth(node) {
    if(!node) return 0
    return Math.max(getDepth(node.left),getDepth(node.right)) + 1
}