将有序数组转换为二叉搜索树

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {number[]} nums
 * @return {TreeNode}
 */
var sortedArrayToBST = function(nums) {
  if(nums.length === 0) {
    return null;
  }
  if(nums.length === 1) {
    return new TreeNode(nums[0]);
  }
  var mid = parseInt(nums.length / 2);
  var root = new TreeNode(nums[mid]);
  root.left = sortedArrayToBST(nums.slice(0, mid));
  root.right = sortedArrayToBST(nums.slice(mid+1));
  return root;
};