index.js

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */

function maxDepth(root) {
  //排除[] --> null空树
  if (!root) {
    return 0;
  }
  let depth = 0;
  //Math.max([]) --> -Infinity错误
  let arr = [0];

  function getDepth(root, depth) {
    //层级
    depth++;
    if (root.left) {
      getDepth(root.left, depth);
    }
    if (root.right) {
      getDepth(root.right, depth);
    }
    if (!root.left && !root.right) {
      //保存每个叶子所在层级
      arr.push(depth);
    }
  }
  getDepth(root, depth);
  return Math.max(...arr);
}

// 数组二叉树算法，不转换为对象
function getMaxDepth(root) {
  let depth = 0;
  let count = 0;
  while (root.length) {
    let val = Math.pow(2, count);
    count = 0;
    for (let j = 0; j < val; j++) {
      if (root[j] !== null) {
        count++;
      }
    }
    depth++;
    root.splice(0, val);
  }
  return depth;
}
module.exports = [getMaxDepth];