Convert Sorted List to Binary Search Tree [LeetCode]

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

Solution:

     TreeNode *sortedListToBST(ListNode *head) {
         if(head == NULL)
             return NULL;
         if(head->next == NULL)
             return new TreeNode(head->val);

         ListNode * current = head;
         int size = ;
         while(current != NULL){
             size ++;
             current = current->next;
         }
         current = head;
         int median = size / ;
         int count = ;
         ListNode * median_node = NULL;
         ListNode * pre_node = NULL;
         while(current != NULL){
             if(count == median){
                 median_node = current;
                 pre_node->next = NULL;
                 break;
             }
             count ++;
             pre_node = current;
             current = current->next;
         }
         TreeNode * root = new TreeNode(median_node->val);
         root->left = sortedListToBST(head);
         root->right = sortedListToBST(median_node->next);
         return root;
     }