230.二叉搜索树中第k小的元素.js

/*
 * @lc app=leetcode.cn id=230 lang=javascript
 *
 * [230] 二叉搜索树中第K小的元素
 */

const { traverse } = require('@babel/core')

// @lc code=start
/**
 * 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
 * @param {number} k
 * @return {number}
 */

var kthSmallest = function(root, k) {
  let res = 0
  let count = 0
  traverse(root, k)
  return res
  function traverse(root) {
    if (!root) return
    traverse(root.left)
    count++
    if (count === k) {
      res = root.val
      return
    }
    traverse(root.right)
  }
}

// @lc code=end

module.exports = { kthSmallest }