LeetCode Reverse Nodes in k-Group

Question

was trying out this LeetCode question

https://leetcode.com/problems/reverse-nodes-in-k-group/

The output supposed to be [3,2,1,4,5] but I keep on getting [3,2,1,4]. I believe there's problem with my current pointer but couldn't think stop it from referring to head.

I'm new to C++ by the way. Any assistance would be greatly appreciated.

class Solution {
public:
    ListNode* reverseKGroup(ListNode* head, int k) {
        // head = [1,2,3,4,5]
        k = 3;
        cout << "RECURSE" << endl;
        ListNode* current = head;
        ListNode* next = NULL;
        ListNode* prev = NULL;
        for(int i = 0; i < k; i++){
            if(head == NULL){
                return current;
            }else{
                next = head->next;
                head->next = prev;
                
                prev = head;
                head = next;
            }
        }
        
        current->next = reverseKGroup(head, k);
        return prev;
    }
};