detect a loop in linked list using hashing

1. HASHING

#include <iostream>

#include <bits/stdc++.h>

using namespace std;

//hashing to detect a  loop in a linklist

struct node{

    int data; struct node* next;

};

void push(struct node** head_ref, int new_data)

{

    struct node* new_node= new node(); new_node->data= new_data;

    new_node->next= (*head_ref); (*head_ref)= new_node;

} //f ends

//returns true if a loop is detected

bool detectloop(struct node* hash)

{

    unordered_set<node*> set;

    while(hash!=NULL) {

        if (set.find(hash)!=set.end()) return true;

        set.insert(hash); //if we are visiting a new node , insert in hash

        hash= hash->next;

        

    } //while ends

    return false;

} //bool ends

int main() {

 struct node* head= NULL; //start with empty linkedlist

 push(&head, 20);

  push(&head, 4);

   push(&head, 15);

    push(&head, 10);

 

   //create a loop for testing

   head->next->next->next->next=head;

   if(detectloop(head)) cout<< "Loop found";

   else cout<< "No loop here";

return 0;

}