108. 将有序数组转换为二叉搜索树

/**
 * 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 {number[]} nums
 * @return {TreeNode}
 */
var sortedArrayToBST = function (nums) {
  if (nums.length === 0) return null
  let mid = Math.floor(nums.length / 2)
  if (mid < 0 || mid >= nums.length) {
    return null
  }
  let root = new TreeNode(nums[mid])
  root.left = sortedArrayToBST(nums.slice(0, mid))
  root.right = sortedArrayToBST(nums.slice(mid + 1))
  return root
}