Reverse linked list

#include <iostream>

using namespace std;

struct Node
{
    int data;
    struct Node* next;
} *first = NULL;


void add(int data)
{
    if(first == NULL)
    {
        first = new struct Node;
        first->data = data;
        first->next = NULL;
        return;
    }
    struct Node* p = first;
    while(p->next)
    {
        p = p->next;
    }

    struct Node* t = new struct Node;
    p->next = t;
    t->data = data;
    t->next = NULL;

}

void display(struct Node *p)
{
    while(p)
    {
        cout << p->data << endl;
        p = p->next;
    }
}

void reverseLL(struct Node*q, struct Node*p )
{
    if (p)
    {
        reverseLL(p, p->next);
        p->next = q;
    }
    else
        first = q;
}



int main()
{
    add(10), add(20), add(30);
    display(first);
    reverseLL(NULL, first);
    display(first);

}