Leetcode - 110. Balanced Binary Tree

https://leetcode.com/problems/balanced-binary-tree/

Solution 1

/**
 * 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;
  }
  return checkDepth(root) !== false;
};

const checkDepth = (node) => {
  if (node === null) {
    return 0;
  }

  // 각각 false 혹은 왼쪽/오른쪽 자식의 최대 깊이
  const left = checkDepth(node.left);
  const right = checkDepth(node.right);

  if (left === false || right === false || Math.abs(left - right) > 1) {
    return false;
  }

  // 트리의 가장 깊은 길이를 return
  return Math.max(left, right) + 1;
};