<p>Given an integer array <code>nums</code> where the elements are sorted in <strong>ascending order</strong>, convert <em>it to a </em><span data-keyword="height-balanced"><strong><em>height-balanced</em></strong></span> <em>binary search tree</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/btree1.jpg" style="width: 302px; height: 222px;" />
<pre>
<strong>Input:</strong> nums = [-10,-3,0,5,9]
<strong>Output:</strong> [0,-3,9,-10,null,5]
<strong>Explanation:</strong> [0,-10,5,null,-3,null,9] is also accepted:
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/btree2.jpg" style="width: 302px; height: 222px;" />
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/btree.jpg" style="width: 342px; height: 142px;" />
<pre>
<strong>Input:</strong> nums = [1,3]
<strong>Output:</strong> [3,1]
<strong>Explanation:</strong> [1,null,3] and [3,1] are both height-balanced BSTs.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>4</sup></code></li>
	<li><code>-10<sup>4</sup> &lt;= nums[i] &lt;= 10<sup>4</sup></code></li>
	<li><code>nums</code> is sorted in a <strong>strictly increasing</strong> order.</li>
</ul>

/**
 * 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* sortedArrayToBST(vector<int>& nums) {
        if (nums.empty())
            return nullptr;
        int mid = nums.size()/2;
        TreeNode* node = new TreeNode(nums[mid]);
        if (nums.size() == 1)
            return node;
        else if (nums.size() == 2) {
            TreeNode* leftNode = new TreeNode(nums[0]);
            node->left = leftNode;
        }
        else {
            vector<int> subL(nums.begin(), nums.begin() + mid );
            vector<int> subR(nums.begin() + mid + 1, nums.end());
            node->left = sortedArrayToBST(subL);
            node->right = sortedArrayToBST(subR);
        }
        return node; 
    }
};
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