leetcode 108. Convert Sorted Array to Binary Search Tree

 1 TreeNode *sortedArrayToBST(vector<int> &num) 
 2     {
 3         return BSTtranslate(num, 0, num.size() - 1);
 4     }
 5     
 6     TreeNode *BSTtranslate(vector<int> &num, int left, int right)
 7     {
 8         TreeNode *root = NULL;
 9         if (left > right)
10             return NULL;
11         
12         int middle = (left + right) / 2;
13         root = new TreeNode(num[middle]);
14         root->left = BSTtranslate(num, left, middle - 1);
15         root->right = BSTtranslate(num, middle + 1, right);
16         return root;
17     }