Detect Cycle

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

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

void push(struct Node **head, int newData)
{
    struct Node* newNode = new Node;
    newNode->data = newData;
    newNode->next = (*head);
    (*head) = newNode;
}

void deleteList(struct Node** head)
{
    struct Node *curr = *head;
    struct Node *next;
 
    while (curr != NULL)
    {
        next = curr->next;
        free(curr);
        curr = next;
    }
   
    *head = NULL;
}

bool detectCycle(struct Node *head)
{
    struct Node *slow = head, *fast = head;
    while (slow && fast && fast->next)
    {
        slow = slow->next;
        fast = fast->next->next;
        if(slow == fast)
            return true;
    }
    return false;
}


int main()
{
    struct Node *head = NULL;
    push(&head, 10);
    push(&head, 30);
    push(&head, 90);
    push(&head, 50);
    head->next->next->next->next = head;
    if(detectCycle(head))
        cout<<"\nCycle is present";
    else    
        cout<<"\nCycle is not present";
    return 0;
}