Convert Sorted Array to Binary Search Tree

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example: Given the sorted array: [-10,-3,0,5,9],

One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
      0
     / \
   -3   9
   /   /
 -10  5

Solution: Using Binary Search

TreeNode* sortedArrayToBSTUtil(vector<int>& nums, int left, int right) {
    if (left > right) return NULL;

    int index = left + (right - left)/2;
    TreeNode *head = new TreeNode(nums[index]);
    head->left = sortedArrayToBSTUtil(nums, left, index-1);
    head->right = sortedArrayToBSTUtil(nums, index+1, right);
    return head;
}

TreeNode* sortedArrayToBST(vector<int>& nums) {
    return sortedArrayToBSTUtil(nums, 0, nums.size()-1);
}