Convert Sorted Array to Binary Search Tree

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

    TreeNode *sortedArrayToBST(vector<int> &num) {
        if (num.size() == 0)
            return NULL;
            
        return sortedArrayToBST(num, 0, num.size()-1);
    }
    
    TreeNode *sortedArrayToBST(vector<int> &num, int begin, int end){
        if (begin > end)
            return NULL;
            
        int mid = begin + (end - begin)/2;
        TreeNode* node = new TreeNode(num[mid]);
        node->left = sortedArrayToBST(num, begin, mid - 1);
        node->right = sortedArrayToBST(num, mid + 1, end);
        
        return node;     
    }