將升序陣列轉為高度平衡的二叉搜尋樹

eg:
Input: nums = [-10,-3,0,5,9]
Output: [0,-3,9,-10,null,5]
Explanation: [0,-10,5,null,-3,null,9] is also accepted:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* binarySearchTree(vector<int>& nums, int left, int right){
        if(left <= right){
            int middle = (int)((left+right)/2);
            TreeNode *t = new TreeNode(nums[middle]);
            t->left = binarySearchTree(nums, left, middle-1);
            t->right = binarySearchTree(nums, middle+1, right);
            
            return t;
        }else{
            return nullptr;
        }
    }
    
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        if (nums.size() == 0)
            return nullptr;
        else{
            return binarySearchTree(nums, 0, nums.size()-1);
        }
    }
    
};