question110.js

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
let isBalanced = function (root) {
    if (root === null) {
        return true;
    }
    let left = depth(root.left);
    let right = depth(root.right);
    return (
        Math.abs(left - right) <= 1 &&
        isBalanced(root.left) &&
        isBalanced(root.right)
    );
};
let depth = function (node) {
    if (!node) {
        return 0;
    }
    return Math.max(depth(node.left), depth(node.right)) + 1;
};

// let isBalanced = function(root) {
//     return recur(root) !== -1;
//     function recur(root) {
//         if (!root) {
//             return 0;
//         }
//         let left = recur(root.left);
//         if (left === -1) {
//             return -1;
//         }
//         let right = recur(root.right);
//         if (right === -1) {
//             return -1;
//         }
//         return Math.abs(left - right) < 2 ? Math.max(left, right) + 1 : -1;
//     }
// }