Reverse a Linked List in groups of given size

Given a linked list of size N. The task is to reverse every k nodes (where k is an input to the function) in the linked list. If the number of nodes is not a multiple of k then left-out nodes, in the end, should be considered as a group and must be reversed (See Example 2 for clarification).

• Time : O(n)
• Space : O(1)

c++

struct NodeWrapper {
    node* head;
    node* tail;
    node* nextHead;
    bool succeed;
    
};

class Solution {
    NodeWrapper _reverse(node* head, int k) {
        node* dummy = new node(-1);
        node* tail = head;
        while(k-- and head) {
            node* tmp = head->next;
            head->next = dummy->next;
            dummy->next = head;
            head = tmp;
        }
        
        return {dummy->next, tail, head, k == -1};
    }
public:
    struct node *reverse(struct node *head, int k) {
        node* dummy = new node(-1);
        node* dummyTail = dummy;
        while(head) {
            NodeWrapper wrapper = _reverse(head, k);
            
            dummyTail->next = wrapper.head;
            dummyTail = wrapper.tail;
            head = wrapper.nextHead;
            
        }
        return dummy->next;
    }
};