Rearrange a given linked list in-place GeeksforGeeks Medium level Linkedlist

#include<bits/stdc++.h>
using namespace std;

struct Node {
	int data;
	struct Node* next;
};

Node* newNode(int key){
    Node* temp = new Node;
    temp -> data = key;
    temp -> next = NULL;
    return temp;
}

void reverse(Node** h2){
    Node *prev = NULL;
    Node *curr = *h2;
    Node *next = NULL;
    while(curr){
        next = curr -> next;
        curr -> next = prev;
        prev = curr;
        curr = next;
    }
    *h2 = prev;
}

void printlist(Node* head){
    while (head != NULL) {
        cout << head -> data << " ";
        if (head -> next)
            cout << "-> ";
        head = head -> next;
    }
    cout << endl;
}

void rearrange(Node** head){
    Node *slow = *head;
    Node *fast = slow -> next;
    while(fast and fast -> next){
        slow = slow -> next;
        fast = fast -> next -> next;
    }
    Node *h1 = *head;
    Node *h2 = slow -> next;
    slow -> next = NULL;
    reverse(&h2);
    *head = newNode(0);
    Node* curr = *head;
    while(h1 || h2){
        if(h1){
            curr -> next = h1;
            curr = curr -> next;
            h1 = h1 -> next;
        }
        if(h2){
            curr -> next = h2;
            curr = curr -> next;
            h2 = h2 -> next;
        }
    }
    *head = (*head) -> next;
}

int main(){
    Node *head = newNode(1);
    head -> next = newNode(2);
    head -> next -> next = newNode(3);
    head -> next -> next -> next = newNode(4);
    head -> next -> next -> next -> next = newNode(5);
    rearrange(&head);
    printlist(head);
}