Counts the number of nodes in a circular linked list

countcirclinkedlist.cpp

#include<iostream>
#include<string>
#include<map>
#include<vector>
using namespace std;

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

void display(Node*head){
    if (!head) return;
    Node* cur = head;
    do {
        cout<<cur->data<<" ";
        cur = cur->next;
    }while(cur != head);
    cout<<endl;
}

Node* nn(int d){
    return new Node{d};
}

int count(Node* head) {
    if (!head) return 0;
    if (head->next == head) return 1;
    Node* rest = head->next;
    head->next = head->next->next;;
    int result = 1 + count(head->next);
    head->next = rest;
    return result;
}

/*
int count(Node* head) {
if (!head) return 0;
}

int count(Node* head) {
    if (!head) return 0;
    int result = 0;
    Node* cur = head;
    do {
        result++;
        cur = cur->next;
    } while (cur != head);
    return result;
}
*/

Node* reverse(Node* head) {
    if (!head || !head->next) return head;
    Node* prev = head;
    Node* cur = head->next;
    do {
        Node* nxt = cur->next;
        cur->next = prev;
        prev = cur;
        cur = nxt;
    } while (cur != head);
    cur->next = prev;
    return prev;
}

int main() {
    auto h=nn(1);
    h->next=nn(2);
    h->next->next=nn(3);
    h->next->next->next=nn(4);
    h->next->next->next->next=h;
    display(h);
    cout<<count(h)<<endl;
}

Create a smaller linked list by removing a node and counting the number of elements in that list.