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 = 0;
        while(current != NULL){
            size ++;
            current = current->next;
        }
        current = head;
        int median = size / 2;
        int count = 0;
        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;
    }